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iksobarg

Getting to some decision-making over my first dslr AP kit, help

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I'm using a Pentax k30 and have a good assortment of (more) older and (few) newer lenses. Over the past month I've been reading from many, many  sources: the forum here, some German sites and lots of others,namely a site/pdf article by two avid dslr AP http://www.project-nightflight.net/Astrotrac_Astrophotography_with_DSLR.pdf and a youtube video helped me get right to the point


but not final decision to give it a go with my camera/lenses and either a Pentax O-gps1 ($200)http://www.pentaxforums.com/accessoryreviews/pentax-o-gps1.html , astrotrac (~$700) http://www.project-nightflight.net/Astrotrac_Astrophotography_with_DSLR.pdf , or ioptron (~$500) http://www.dpreview.com/forums/post/51452441 I'm still pinpointing a real astro lens. So far I like the William Optics 71mm ED (~$500), http://www.amazon.com/William-Optics-ZenithStar-Refractor-Flattener/dp/B00GS5OFZM/ref=sr_1_6?s=electronics&ie=UTF8&qid=1388618316&sr=1-6&keywords=williams+telescope and a few others.

Important: I'm also now researching some Sigma APO for Pentax Dslr lenses for astrophotography. Are Sigma APO lenses distinctly better than older, say Pentax SMC, or other older m42 lenses? (I'm researching this now).

Also, I'm having trouble finding the proper mount for a dslr with any of the tracking systems I mentioned. The mount would need to be able to handle the lens you talk of: the 72mm size OTA.

My last question:
Besides the mount, telescope+flattener/dslr lens, tracking device, dslr camera, what all additional kit am I going to need? , 45/90 diagonals(?)...

I'm in such a flux about some things and expect to get a really refined list of what all is really going to work.
Help and thanks!!

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I'm using a Pentax k30 and have a good assortment of (more) older and (few) newer lenses. Over the past month I've been reading from many, many  sources: the forum here, some German sites and lots of others,namely a site/pdf article by two avid dslr AP http://www.project-nightflight.net/Astrotrac_Astrophotography_with_DSLR.pdf and a youtube video helped me get right to the point

but not final decision to give it a go with my camera/lenses and either a Pentax O-gps1 ($200)http://www.pentaxforums.com/accessoryreviews/pentax-o-gps1.html , astrotrac (~$700) http://www.project-nightflight.net/Astrotrac_Astrophotography_with_DSLR.pdf , or ioptron (~$500) http://www.dpreview.com/forums/post/51452441 I'm still pinpointing a real astro lens. So far I like the William Optics 71mm ED (~$500), http://www.amazon.com/William-Optics-ZenithStar-Refractor-Flattener/dp/B00GS5OFZM/ref=sr_1_6?s=electronics&ie=UTF8&qid=1388618316&sr=1-6&keywords=williams+telescope and a few others.

Important: I'm also now researching some Sigma APO for Pentax Dslr lenses for astrophotography. Are Sigma APO lenses distinctly better than older, say Pentax SMC, or other older m42 lenses? (I'm researching this now).

Also, I'm having trouble finding the proper mount for a dslr with any of the tracking systems I mentioned. The mount would need to be able to handle the lens you talk of: the 72mm size OTA.

My last question:

Besides the mount, telescope+flattener/dslr lens, tracking device, dslr camera, what all additional kit am I going to need? , 45/90 diagonals(?)...

I'm in such a flux about some things and expect to get a really refined list of what all is really going to work.

Help and thanks!!

Hi,

First you need to decide what it is you want to image, then what you want to image with? DSLRs ( mostly Canons ) are a popular entry for wide field DSO imaging coupled to something like an SW 80 ED or a 130 ~ 150 mm aperture fast newtonian. The most critical part of the chain is the mount BTW, not the scope or camera. A TAK 106 is of no use if the mount is wobbly and can not track properly. You must also accept that there is no such thing as a universal imaging scope, most of us end up with atleast two or three scopes to deal with different subjects.There is also a good  book called make every photon count and it will help you understand what is required and what can or can not be done, it is worth a read.  I would be very careful about buying a lens designed for terrestrial use as a DSO imager due to the uncorrected CA at wide open aperture, for the price of the ones you are looking at a nice Doublet or even an Apo triplet scope could be purchased , however a Canon 200 mm F2.8 L or a Nikon 180mm F2.8 ED are very popular for ultra wide field imaging using either a DSLR or a CCD coupled with a suitable adapter but these are rather specialised applications and expensive to say the least.

Good Luck,

A.G

Edited by lensman57

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Well using lenses and using a telescope are two different things and require different setups. 

If you are going to use just lenses then all you need is the astrotrac and a good standard camera tripod. They offer a pier for it, see their website, but thats not a must. If you want to use a dedicated telescope then you might have to jump to an actual mount because of the weight. Now maybe the astroctrac can handle the weight of a small telescope (60mm or so I believe is the limit) you'll have to check the specs. But by the time you buy the scope and the FF/R I think you might as well just go with a good APO lens. Not only is the weight lighter but you will have more options in focal lengths. 60mm refractors have such a short FL, especially when you add a FF/R on it, that its very comparable to common lens FL. My ED80 with my FF/R has a FL 380mm and is WAY heavier than a 400mm lens and has a slower f/ratio. 

You wont need any diagonals for imaging with a scope. If you want the right angle view finder then thats up to you but its not NEEDED. You will need a T-adapter and spacer so you'll have enough back focus to achieve focus. This is for the telescope only btw.

Not sure what your light pollution is like but if its pretty bad you'll want to look into a LP filter. The have several for DSLRs. But if you are wanting to use lenses then don't get the clip-in filters as it will stop you from attaching any lenses to the DSLR. 

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Thanks for your responses/feedback guys. I've ordered making every photon count. As for the DSLR setup; that's for wide stuff only, that is what is possible, def. no dsos, I know. I'd like to just use what I have until I've got the basics down and that means learning how to use DSS properly. I realize I might've lowering the bar so to speak but I'm in no hurry to make purchases. This oughta be a good drawn out matter for me as I'm also coming to terms with how much I have to learn AND the amount of money I'm going to be dropping someday.

The idea of the 72mm refractor came from the YouTube vid. above. I like the fact that it was a pretty straightforward pitch about refractors being ideal for imaging, which I'm sure might be a point of contention in some circles. That setup he called for in the vid. also called for a reducer and special camera. It might appear naive on my part but I'm not particular about exactly what i image. I'm more of the nature of using what is going to get me out there and learning imaging. I'm new to this world and truly thankful for guidance.

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Wide field isn't determined whether you use a refractor or a camera lens. Its determined by the focal length. A 300mm lens and telescope will get you the same field of view on the same camera. The one thing you have to worry about is if they are color corrected properly. For lenses you will need to look into it and this usually means APO lenses. Other wise you'll get purple halos around your stars. For scopes it means you will want Apo scopes and not Achro scopes for the same reason. 

DSS is actually pretty easy to learn. What you will want to really learn is Photoshop or similar software for the post processing. DSS just stacks and combines your multiple images with little data into one image with lots of data. Then you switch to PS (or similar) and bring out all that data to show the full extent of what you collected. 

If you are looking to take it slow but eventually want to really get into serious AP then I would suggest to skip the Astrotrac and go for a mount. Stick with the DSLR and lenses for now. You will be able to attach the camera and lens to it like you would a telescope. This will allow you to get use to the mount and camera and all the software. Then if you are still liking the hobby then you can get to buying a nice scope. The only reason I would get an Astrotrac is A: If you have no intent on getting a telescope and sticking to ultra wide field to semi wide field AP. By this I mean using 12mm to 400mm lenses. And B: If you are in very bad LP area and have to travel to remote dark sites or just travel a lot. The Astrotrac is very portable and easily fits in the over head on a plane where a mount doesnt do that so well.

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Short-term: Though I'd love to I'm not ready to change over to Canon. I'm for using my current DSLR for now, with the addition of a real APO lens.  Fortunately Sigma produces many APO lenses.  I do need to read more about these lenses being appropriate for AP. If so then I would choose a prime in some starter-relevent focal length. I'm not sure them make a prime 70mm but I know they have many zooms that would cover it. Thanks for pointing out how much longer focal lengths present problems with tracking. I'm trying to be careful not to get over my head!
 
Also, I've read here: http://www.cloudynights.com/item.php?item_id=2868  , that older m42 screwmount lenses are also good, but the article provided no basis for why. I'm going to contact the good people who authored this article about this and/or do more research.
I have two normal tripods but still need a mount and if the Astrotrac appears ideal I'll likely bite sometime soon.
 
Longterm:
Since I'm not particularly fixed on what I want to image would a 72mm APO telescope (refractor) be a good place to start? Cost has a bit to do with going with a 70-ish focal length.
I'm looking for refractors now and am open to suggestions but need more importantly an ideal computerized EQ mount.
Back to my research. Thanks for you help, gents!!

Clear skies be upon you!

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Theres nothing wrong with stick with your camera. Maybe its noiser maybe not. I'm not sure. But darks will take care of most of it. Also you can just keep your subs shorter to help combat noise. Theres plenty of ways to do that. Canon is just popular because there are more software that are written for it. You'll have to check which software works with your camera. Most should but I would double check. Theres also plenty of lens choices out there. I dont use them so I cant suggest any to you. But you'll want to look for a fast one. Like F2.8. This will help you keep your subs short and noise down. 

For your long term: If you are wanting seriously to get into AP then the most tried and tested and proven mount is the HEQ5. There are a couple mounts below it, price wise, but there are issues you will have to over come when you drop down. When you choose the 70ish mm refractors you are pretty much choosing what you want to image. Wide field AP. This will be mostly nebula and a few other larger objects. Most the small objects like galaxies and planetary nebula will be too small to get a lot of detail out of. Not that you cant image them just you wont be seeing lots of dust lanes and such. To get a good idea of the scale that you'll be imaging at is by going to Astrobin and searching for the telescope you are planning on using and see what images people have taken with it. 

Most people start off in wide field AP, myself included. Its the best way to enter AP as it will be the fewest problems. Longer the focal length the more expensive the equipment and the more problems.

Definitely read the book Make Every Photon Count. It will clear up A LOT for you.  

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Well I did some homework today and decided to not decide on anything...

Just kidding. Well, not really.

In my ongoing investigation I uncovered this little gem of an article about review/shootout between Vixen Polarie, Astrotrac and Ioprton Skytracker DSLR tracking systems. The article is by David Woods and Sharon Rose of ioastronomy: http://www.ioastronomy.co.uk/2013/07/astrotrac-vs-skytracker-vs-polarie/

Just a note: "Making Every Photon Count" by Steve Richards is not avail. here in Germany.  Shipping cost from the Uk is making me sad but I'll get over it. I know you guys will say it's worth it :)

So my long term plans for a larger setup are effectively shelved so I can truly get up to speed on the ABCs of AP imaging.

I've done some light math and am not sure I can justify the expense anytime soon. I still have the idea of , a goto-HEQ5 (as recommended) loaded with a 72mm ED APO fitted for DSLR. It might take a few years but that's fine. I should be ready for it with some good DSLR AP experience.

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I had a crescendo early this morning: So it was a few months ago that I checked the Pentax Astrotracer here: http://www.pentaxforums.com/reviews/pentax-o-gps1-gps-unit/sample-astrophotography.html I've known about this unit for at least a year+ but along with my interest in astronomy and AP I shelved it due to a new baby, work, etc.
The sample pics turned me off and I gave up on this trail.

Now recently I found an old Pentax k5 Astrotracer related thread that has thrown this little device back onto my list: http://www.pentaxforums.com/forums/38-photographic-technique/199177-astrophotography-astrotracer-worth.html
Some of the pictures have blown me away: http://www.pentaxforums.com/forums/115-pentax-k-5/143409-k-5-astrophotography-11.html#post2134702
While I think my first pictures are likely to look like the first link above (they look to be with little or no PP), I'm wondering how great of a PP artist I am going to have to become!

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