Parfocal filter test #1

I always wondered this, but as I didn't have a motorized filter with readable steps (until now) I wasn't able to do any testing on my filters previously. Since the moon is lovely and bright tonight killing most of my imaging plans I figured I would do some focus tests with my new Moonlite focuser. After letting the scope cool to the nice chilly evening (whilst my toes froze nice and solid as well) I ran through my Astronomik set (LRGB and Ha,SII,OIII) and not only did FocusMax's "focus" button but then dug around a few steps each way to find the best focus for each filter. Happy to say that the "focus" button on FocusMax got the focus within 1-2 steps of best focus so gotta say that I am happy to use the automated routine in the future. 

Now for the results. 
Filter set: Astronomik Type IIC broadband and narrowband filters
Scope: Orion EON80ED
Camera for testing: Atik 314L+
Moonlite Focuser
Filter Wheel: Atik EFW2
Camera temp: -20C
Ambient temp at time of test: 3.3C

Position at "best" focus for each filter at time of testing: 
Lum: 10681
Red: 10679
Green: 10676
Blue: 10719
Ha: 10683
SII: 10686
OIII: 10683

All in all, I say that is pretty good (except for the blue filter of course, which I knew already had issues) ... All others were within 5 steps of each other with the Luminance being pretty well centered between them. I am happy to see how close to parfocal all 3 narrow bands are and how close they are to the Luminance. 

With that said, I do have an Astrodon LRGB set on the way and will be interested to see how they perform (at the moment I am staying with the Astronomik NB as I have been happy with them but the Blue on my Astronomik set drives me nuts and if I am gonna change one might as well get the whole set. Once they arrive I plan on doing the same test with them as well and will post those results.


After a few more rounds of testing I will have a reliable focus offset for each filter so I can add that to my automated routine, which should make automated routines easier to setup. 


Addition: I got out today and pulled out the caliper to do some measuring. 
On my system, the Moonlite Focuser moves 16 microns/step (determined by multiple tests by moving the focuser 100, 250, 500, 1000 steps multiple times and measuring the distance moved/#steps and averaged out the #, although almost all of the measurements were right at 16 so any differences were likely user error on the caliper)


Next, some math to determine the critical focus zone (CFZ). 
Formula: CFZ=4.88*λ*f ² 
Where λ  is the wavelength of light and f(squared) is the focal ratio of the system squared. 

So, for my f/6.25 system the CFZ is:
Red: 124 microns
Green: 97 microns
Blue: 91 microns


Based on the measurements I did that showed each step was 16 microns, the CFZ in steps for each color (rounded down) is:
Red: 7 steps
Green: 6 steps
Blue: 5 steps


Not a lot of room for error, only 2-3 steps on either side of the focus point. Makes me even happier that I got the motorized focuser as finding that 91-127 micron sweet spot by hand was exceedingly difficult (even with a Bahtinov mask)

Note: These tests are done on my actual imaging system, not an "ideal" test setup. I find it hard to find results on average setups as "tests" are generally done on apochromatic scopes and very high-end equipment. That is why I like to share my test results on my modest equipment. These are not "scientific" and are done just as I state. I do them for others who have modest setups and would like to find results on setups similar to their own. 

Nikon D7000 for astrophotography: Review

Note: This review can be downloaded as a pdf at: http://www.eprisephoto.com/nikon-d7000.pdf

Although my first astrophotos were taken with a DSLR I quickly steered clear of DSLR astrophotography for a few reasons. First, I use my camera (at the time a Nikon D40) for my regular photography jobs and therefore was not going to get it “astro-modded”. Second, it was beyond noisy. Rather than having a field of stars with a few hot pixels, images were coming out as a field of hot pixels resembling a children’s paint splatter painting with a few stars and perhaps a galaxy thrown in for good measure. Dark frames helped, but even proper calibration only did so much for the overly noisy images. Third, I found a used ccd camera for a good deal and after trying it out once, despite the limited FOV from a small chip, found it much better in terms of image quality and lack of noise. I see fantastic results from DSLRs so I know it can be done, but my few experiences had been nothing more than an exercise in frustration. Fast forward a few years and I found myself upgrading to a Nikon D7000 camera. At the time, I had no thoughts of resuming DSLR astrophotography when I purchased it, but after a few months I decided to give it a go. 

Testing out the D7000: 

After attaching the D7000 to my scope and setting up the DSLR-USB IR sensor so I could set up a sequence via the computer I set about focusing. The D7000 has “Live View” which I was going to use for focus but once I switched to it I realized that while I could see the star I wanted to focus on, it was going to be too dim to accurately focus. I was able to get it close but then switched the live view off, put on the Bahtinov mask, and took a 2 second exposure. It was close enough that it only took me a few moments to fine tune the focus and lock the scope. I found the guide lines in the viewfinder when the shutter is pressed (which light up a dim red) very useful for framing my intended target of the night, M31. I set my ccd up as an autoguider and set “DSLR Shutter” (the program I use on the computer to control the IR sensor on the DSLR-USB IR to take a 10 min exposure and ... nothing. No shutter click to let me know the image had begun. I had the menu settings to “Quick Response Remote” but the D7000 has a roll bar underneath the left selector wheel (where you select M for manual, Auto, etc) that you also have to roll over to the remote picture. Once I had done that, I reset “DSLR Shutter” and off it went. 10 minutes later I checked the result and was pleasantly surprised. At ISO400 (I kept the ISO fairly low since the moon was going to be coming up soon and because I was used to a VERY noisy DSLR in the D40) the image was crystal clear. Andromeda looked great as did the stars and color across the whole image. Obviously the preview screen was always bound to look better than the full-sized image but no glaring problems were obvious so I set “DSLR Shutter” to take a set of 12 ten minute subs and let it shoot. I went back out 2 hours later to find that battery hadn’t even drained 1/4 of the way (also a problem I had with series’ with the D40) and I now had 13 subs of M31. I took a few darks for good measure and brought them all in to check out. 

D7000 Settings:

Before I get into the results of the evening I want to give you the settings and menus where I set those for the session. These are the only camera settings I changed, everything else was left to its default and no “in-camera noise reduction” was used. 

Exposure:	M (Manual)	Roll wheel on top left of camera
ISO:	400	Press “ISO” button on left of preview screen, turn roll bar in front of shutter/on-off button
Image Quality:	NEF (RAW)	MENU->Shooting Menu->Image Quality
Shutter trigger:	Quick-Response Remote	Two places: Shooting Menu->Remote control mode->Quick Response Remote, Secondary roll wheel on top left of camera->remote picture
Shutter Speed:	BULB	Right thumb roll bar

Results:

They say a picture is worth a thousands words, so I will show these results I will start by showing you what a single 10 minute dark sub looked like. All I have done to this was convert it from RAW to a tiff file and then used levels to stretch it so you can see the noise pattern (otherwise it looked completely black at this size).The darks look pretty good to me, especially for a 10 minute sub. Once I combined the 6 I took after my session I had a nice Master Dark to use for calibration. 

Before I did that I did a quick process of an uncalibrated single 10 minute sub of M31 just to get a “before”. This is a crop of the edge of the galaxy. No darks, flats, or bias frames and just a few processing steps comprised of levels and curves. 

I was floored that even a single 10 minute sub with a mild amount of stretching had such little noise! Granted it was a cool evening (40 degrees fahrenheit) but the inherent noise of the D7000 is exponentially lower than the older D40.  The noise was so low in the single stretched sub that I went ahead and did a stack of the uncalibrated subs. Hot pixel streaks were very minimal and in a pinch I believe I could even get away without shooting darks on a cool fall/winter imaging evening. 

I did, however, apply the Master Dark to the subs before I brought them over to be de-Bayered, aligned, and stacked for the final processing. I used several programs to compare how the image looked from the raw stack (Registar, Maxim DL, and Nebulosity), all three came out looking fairly decent but I used the Maxim DL stack for the final process as I found it did a better job on the balance of colors from the Bayer matrix. I used solely Photoshop CS5 for the post-processing, although I do have several plug-ins in addition to my own action set that I use for the processing. I ended up not using any noise reduction in the final process. 

Conclusions: 

For a “first light” for the camera, astrophotography-wise, I would have to say that the D7000 has completely changed my opinion of DSLR astrophotography. Not only does the camera produce crisp, clean images that are relatively noise-free (at least compared to my previous experience with DSLR astrophotography), but the efficient use of the battery allows an evening of shooting without having to worry about the battery going out mid-exposure. As I had this only a fairly low ISO setting (400) I might have to try to shoot some fainter nebulosity with a higher ISO in the future and expand my DSLR astro-gallery. All in all - a great camera in the day or night that I would highly recommend. 


Higher Res final image can be found here: http://www.eprisephoto.com/galaxy/h23732f43

I need more power Scotty! . . . aka "How to build the AstroPig 140"

I have been increasingly frustrated by my power tanks lately, mainly in that I have to use 2-3 of them just to get a full night of imaging with my scope, ccd, filter wheel, auto guider, and dew heaters all running. This, and the largest one I have was 17Ah and after multiple moves (and consequently being drained of power for months at a time during the move) they do not like to hold a charge anymore. My solution: build a power box.

I have done a full writeup of my requirements, calculations, parts, and the build which can be found in this pdf document: http://www.eprisephoto.com/power-box-project.pdf

In short, I have made a power box with a 140Ah 12v deep cycle battery, 6 cigarette lighter-type power sockets, a 7 port USB hub, and two 120v GFCI outlets which are hooked to a 450W power inverter.

I have red lights that shine to the side and down to help with navigating around the scope without tripping over anything, a red LED voltmeter on the front panel and a Battery Tender charger built in as well.

The most difficult part of the build was planning (as is typical with projects) partly as I had not done any wiring projects in quite a while and wanted to be thorough planning out the wiring and parts to map sure it will be safe, all work, and as inexpensive as possible. I went with Anderson PowerPoles for the wiring and distribution box so I wouldn't have to do any soldering and so it would make it simpler to fuse and exchange parts as necessary. Although using these did increase my costs it made the wiring portion significantly easier and, to me, well worth the extra expense. Other than these I did a lot of shopping around and made good use of eBay and other internet sites to find parts. The battery was one of the few things I had to source locally but managed to get it delivered for free which was very nice as a 140Ah battery is quite heavy.

It took a few weeks to get all the parts in, build the box, and wire everything but it is all together and running. I learned a good bit between all of the planning stages and testing everything as I was wiring it all together but it was very fun and nice to have a home-built power box!

I was told it looks like a squat little pig so it has affectionately been named the "AstroPig 140"

Feel free to download my pdf and read more in-depth about the build.

Somewhere between a dream and reality .... Atlantis

January 12, 1997: 15 year old me is sitting in the wee hours of the morning with my family on the grass in Florida staring at a platform lit up by spot lights. The excitement builds with each reducing number in a countdown and I watch as 7 astronauts live out my dream: to go up into space. 3, 2, 1, LIFTOFF of the Shuttle Atlantis. STS-81 turns the dark night into an eery green daylight. Getting to actually watch the shuttle launch is an experience I have never forgotten and still nearly brings me to tears just thinking about it. I dug out our vehicle placard and some photos we took of the launch (and me on the tour - I am the goofy one in the hat in the center). Glad I saved the placard from way back then!

14 years later, technology has advanced, time has moved on. I pursued my dream of being an astronaut for a while - I attended and graduated from the US Air Force Academy in those pursuits. Dreams rarely play out the way you hope and the years have certainly dampened my pursuit of that particular dream although I still desperately would love to go into space I now have a family and am traveling and living around the world with the military. I got out of the Air Force and am now an amateur astronomer/astrophotographer and mother. The former keeping my head in the stars and the latter keeping me firmly planted on Earth. NASA has changed and the shuttle is nearing the end of its magnificent life. One last Shuttle launch. Atlantis flies once more. STS-135 is set to take off on July 8, 2011 and I cannot express how much I wanted to see the Shuttle launch one more time. The past 14 years have kept me busy and unable to return to the Florida coast for this despite many attempts to do so.

NASA has embraced the social media craze that has engulfed our society. They now hold Tweetups where they invite a fortunate few followers from Twitter to attend once-in-a-lifetime events held at various NASA facilities throughout the country. VIP tours, talks from engineers, scientists, astronauts, behind the scenes first-hand looks at the inner workings of NASA. In short, the best 2 days ever for a Space geek like me! I heard about these shortly after I joined Twitter and began applying for the launch ones as well as the ones held at Johnson Space Center. I was living in Texas at the time and had planned to go see Mission Control before we moved regardless but fate intervened and accepted me to the STS-132 JSC Tweetup. I have blogged about that experience  and still get giddy when I remember it or look at my pictures. Sitting in the chair of the Flight Director for the Apollo missions, getting to see astronauts train in the NBL ... SQUEEE!!! :) I was never one of the fortunate ones, however, picked to see a launch from the Press Box and get the inside tour of Kennedy. As the Shuttle's lifespan comes to a close it has gained popularity and each Tweetup got more and more applicants. We were down to the final launch. I had moved to England again with the Air Force so being able to drive over to see it regardless became difficult. I applied for the Tweetup regardless as well as for tickets for the launch. Why not, right? The odds were not in my favor but I had to do it anyways. Despite telling myself that I should not get my hopes up, I did. So when I got the rejection letter for tickets I was a bit bummed. Then the day for Tweetup selections came and went and not only did I not get an acceptance email, I got NO email whatsoever. They send out at least rejection letters regardless so I was beginning to think my application didn't go through - I was a bit upset but went ahead and sent them a message inquiring, just in case.

A response via Twitter raised my hopes again: "You're on the waiting list for #NASATweetup. We'll look into where the email might have gone."  Not accepted, but not rejected!!! 5500 people applied. Only 150 got the invite with another 150 being Wait-listed. Odds were still not great, but I had made the first cut!!! A week came and went with me following all the excitement of those selected and trying to join in - this was an exciting event whether I got to be there or not! As the #s of original invitees creeped up I realized that it was not looking good. I resigned to the fact that I wouldnt be going to the Tweetup but was going to still be excited about the launch, follow those who were going, and enjoy the last launch of the Space Shuttle.

I go out to an afternoon date with my husband while my daughter is in nursery school since he has a random Friday off. Enjoyable afternoon - nice lunch and good movie. All thoughts of NASATweetup are temporarily gone .... until I get home and check my email. This is staring at me from my inbox:

Pretty sure I did some weird convulsive jump and squeal as my husband asked what had happened. I couldn't believe it - I get to go to the last Shuttle Launch!!!!

photo credit: Nathan Bergey

I am working out all the details to attend now, but am still a bit in shock. Look for more from my blog around the 7-8th of July as I make my way to the Space Coast and watch Atlantis leave Earth for the last time. For two days in early July I get to get as close as I can to my dream - the Countdown Clock - and watch the last US Space Shuttle lift off away from its home planet. GO STS-135!!!

The argument about Bias Frames

Until now I have not really used bias frames in my preprocessing (I attempted on the first few imaging attempts ever since I was told I should but quickly stopped using them). I decided to shoot some with my last imaging session and have been trying to compare whether or not they helped at all in the image. 

I did the exact same processing from stack to finish on all three variations except how the bias frames were applied. The first comparison set is just a center crop of M51 from my full frame.

-The first one has no bias at all
-The 2nd had bias frames preprocessed on both the flat and dark frames themselves as well as the preprocessing for the light subs 
-The 3rd had bias frames preprocessed on just the flat and light subs

So the 1st and 3rd appear identical (even when blinking between the two on a super-zoomed level) The 2nd seems the worst, which is what I suspected as I had been told if you add the bias to both the light and dark in Nebulosity it will basically add it back in. 

From this comparison (and the 200% crop) it really almost doesn't seem worth it.


However, since I posted this observation on various astronomy forums I frequent I have all but gotten "shot at dawn" as one guy so eloquently put it. I have been told that flats WILL NOT work if you don't apply bias frames to them (interesting since I have not used bias frames since I started imaging and my flats have been working perfectly well) ... I have also been told that I really only need them if I am going to use scaled darks, which makes much more sense to me than the "nothing will work right if you don't use them" argument. 


Seeing as they take almost no time to shoot and add into my pre-processing steps I might as well use them to avoid further ridicule but seriously - see if you can really tell a difference in these 100% and 200% crops of the M51 image I am currently imaging. 

Also, according to Ron Wodaski's "The New CCD Astronomy", pg 244: 
"The sole purpose of a bias frame is to allow you to use dark frames whose exposure time does not match the light frame exposure time. If you always take dark frames with the same exposure as your light frames, you do not need to take bias frames" .... 


Since I don't use scaled darks this explains my results and I am officially ignoring all the contradictory and argumentative (& some downright rude) comments I have been getting to this question on my astronomy forums. 

Behind the scenes, at NASA!

Earlier this week my husband and I were fortunate enough to attend NASA's latest Tweetup at Johnson Space Center. What is a Tweetup? Well, it is a gathering of Twitter followers of course. NASA has been putting them on recently to gain publicity and awareness of launches, programs, etc. Myself (@antimorris) and my husband (@vtmath) traveled the short distance to Houston for a full day at the home of astronaut training, Johnson Space Center.

We were greeted with nametags, coffee, and an hour or so to explore the Visitor Center before it was open to the public. It was very nice to see the exhibits without the noise of crowds and enthusiastic children (although I think all of us at the Tweetup were just as, if not more, enthusiastic about this than all the children!) ... after the initial free-time we all gathered in the auditorium for some briefings. These, mind you, are not your typical boring briefings. We were treated to a backdrop of the live EVA going on up on the ISS and talks from astronauts Ellen Ochoa & Jeff Williams as well as a very in-depth break-down about the new Ku-band communications antenna that was being installed by the EVA in the background. All of these "briefings" were very much audience focused and the majority of the time was spent on Q&A rather than just being talked at. I think we all thoroughly enjoyed Jeff Williams (@Astro_Jeff) describing the differences in launch and landing in the Soyuz versus the Shuttle, just how excited all the astronauts are that they now have internet up on the Space Station, and their new exercise equipment up on the ISS. 

We then had time for a quick lunch in the VC cafeteria and then broke our 100 person group into two to start the tour. This was, mind you, not the typical tour you get when you visit JSC! We first headed over to Mission Control ... yes, THE MCC which was currently running STS-132. We got to sit in the gallery and watch them finish up the EVA and have Ed Van Cise (@Carbon_Flight), a Flight Director for the ISS, speak to us.

If this wasnt enough, we then made our way through the labyrinth that is Building 30 down to the historic Apollo Mission Control. Why Annie, you might say, the Apollo Mission Control is on the regular tour. Well, yes, and no. Normally you get to go to the gallery for the Apollo MC and just look in the room, we got to go in the room, press buttons, sit in the Flight Director's chair and wave back at the people on the "regular tour" in the gallery. It was fantastic!

This day couldnt get any better, right? .... WRONG! Where we headed to next was the place I have been wanting to see for years and was the most excited about (although MCC was pretty darn neat!) ... The Neutral Buoyancy Lab (NBL)! Thats right, the ridiculously giant, perfectly clear swimming pool with life-size shuttle cargo bays and the ISS in parts in it so astronauts can train on them. To make it even better, there were multiple astronauts in the pool (each with 4 safety divers) training when we were there. This massive training facility is beyond description. The only thing that would have made it better was to have been able to go diving in the pool, but alas, only NASA-certified divers are allowed.

By this point, I am beyond a happy camper. But we are still not done with the tour! We next head over to the Space Vehicle Mockup Facility (SVMF) to see the shuttle, Soyuz, and ISS trainers. We, of course, get an astronaut tour-guide, Dave Leestma, and also get to see STS-133 crew as they practice their post-liftoff suiting procedures. In this building they also have the new Lunar Electric Rovers, and some other robotic prototypes for future space operations. All very neat to see. 

We then capped off the day with a visit to the Rocket Park and the Saturn V rocket, which I have seen many times but am still impressed by its size every time I do. 

My overall impressions for the day ... WOW ... oh and never did I think that Twitter would be so useful. Getting to watch Mission Control run a shuttle flight, see astronauts train in the NBL, chat with multiple astronauts, and everything else we did were just amazing. Thank you Johnson Space Center and NASA for the behind-the-scenes look at everything. As someone described during the day, it was like having the golden ticket to get a special tour of the Willy Wonka's chocolate factory. It was a fantastic day and I really hope that we are fortunate to do another Tweetup with you in the future (preferably to a shuttle launch, hint hint)

Click on any photos here to see them larger or if you want to see all of my photos from the day, they are located here: STS-132 Tweetup Photos

Polar Alignment at last

A bit more tweaking and I finally got my polar alignment so I can take 5 minute subs with no autoguider. YAY! I have spent the past few nights getting data on M101 - the luminance came out well but I think my focus was off for my RGB, but at least I have a decent result - I will go back and get more color at some point:

More polar alignment fun

Spent another night working on my polar alignment - its getting better. Finally was able to get an unguided 85sec image (keep in mind I did short sets of only 30min per channel as I was just testing my alignment) of M51 "Whirlpool Galaxy".

I still have a little polar alignment work and the next clear night I am going to give drift alignment a try, and then add in autoguiding which I tested the other day and looks like it will work well.

I am definitely looking forward to the future of my astroimaging now that I have a wedge for polar alignment and an autoguider .... until then - here is my first polar alignment image:

My first polar alignment attempt

So my first attempt at polar alignment and working with the wedge were about what I expected, meaning not that great but at least I learned alot. Though at least with the clouds and the moon I didnt feel like I was wasting a great observing night. Here's how it went: 

Got it all set up this afternoon and roughly oriented to celestial north (we had previously marked paving stones in the yard that we use for the tripod legs with the directions for celestial navigation) and waiting til dusk. About then I realized I hadnt balanced the scope on the wedge .... um yeah - that went fantastically (sarcastic of course) ... when I balanced on alt-az once I had the piggyback scope it didnt take too long to get a dynamic balance, not the case on the wedge so #1 thing to add to the "do in the daytime" list. I got it close and about that time the stars were becoming visible. 

I started to align the wedge and scope with my polar scope (the arm I made isnt SUPER sturdy (just sheet metal) - so this was just to get me roughly close) ... got close there and got closer using eyepieces. Then I ran through the Celestron Equatorial Alignment sequence (as that is what my manual says to do after you have a close polar alignment). Did that no problems. Then my manual says to do a "wedge align" - only problem is there is no wedge align in the menu .... had to come inside to read that my upgraded firmware replaced that with something else. Check - back out to the scope ..... 

At this point I wanted to see how well I was doing so I put in my Ha filter and slewed to the Horsehead Nebula -- spot on center so yay the alignment mustve been pretty close. I set it for a 60sec image just to gauge how close to a polar alignment I was .... only slight star trails so semi-encouraging. At this point I decided that perhaps I didnt run through the new sequence quite right so I powered down and ran through it all again, this time I added in the "Polar Align" after the "Eq Align" as the new firmware recommends. Slightly off for the polar align sequence so readjusted the mount in that step and then went back to HH to try again ... not center anymore - in fact it was JUST barely in the screen - AW SNAP - mustve not had as great alignment this second go-around ... tried another 60sec image - slightly worse than the first run-through ... GRRR!!! Reassessed and realized I hadnt done the "Polar Align" right. My feet were frozen by this point (note to self - dont wear sandals out on tomorrow's try) so I came in to watch tv and warm up with two giant Great Pyrenees as feet and lap warmers. 

I just went out and put the scope to bed for the night with the following lessons learned: 

1) balance the scope in the daytime ... (and sand that metal bur off the bottom of the counterweight set - I sliced my hand open twice on it tonight)

2) work on the cord situation .... not as much as a problem on alt-az but this extra angle makes the cords quite a mess - fix that in the daytime too

3) reposition polar scope arm ... where I have it gets me close but not close enough ... perhaps move it to the center and just use it before I put the scope on the wedge

4) Dont let the scope auto-pick the alignment stars, at one point i was half-upside down balancing off the fence to get my head where I could see through the finder and eyepiece .... I am not acrobatic so was not very fun

5) be super accurate when aligning so its less error that needs to be corrected in the "polar align" step. 

I didnt expect to get it down pat the first try and be off and imaging 5-10 min subs without an autoguider just on my superb polar alignment skills an hour after attempting it, but got at about 60s subs without really knowing what I was doing so all in all a fairly successful night. I am planning another attempt tomorrow, and if it goes well might get the PEC training for the scope in as well and attempt some autoguiding (my guide camera should be in tomorrow ... though that would mean balancing my piggyback as well - hmmmm come to think of it perhaps that should wait a few more days until this polar alignment thing is slightly easier for me). 

Ok I am done rambling for tonight!