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1st attempt at M51


1st attempt at M51

My first "complete" astro-photo with calibration frames.
30x40 sec exposures, 30 ea. dark, flat, bias frames
Processed in DSS using default settings; GIMP
Nikon D5000, ES N208CF 8" Newt with HP Coma corrector
iOptron CEM40 mount

    Congratulations on your first image!!  It looks like 40 seconds exposures work OK for you with your equipment--stars look small enough and round in the center and corners to the best of being able to tell with this version. Now just add 300 more.... :-)   or try working on your polar alignment (not that you can tell from this if it is close or not....) and/or seeing if you can push your subexposure time a bit (will help cut down on the number of subs you have to process, but at the risk of having to toss more, so it is a bit of a tradeoff--nothing wrong with your exposure time as it is). And leave the background a bit lighter, maybe...oh, one other consideration:  focus with a Bahtinov? or just eyeballing LiveView at 10x?  highly suggest using a mask.

      • belliott4488 likes this
    May 03 2021 08:19 PM

    Yes, I used a Bahtinov mask to focus, but it's difficult with my 12-year-old DSLR's small screen, especially since I used Alkaid, which isn't bright enough to produce long diffraction spikes. I could barely see them on the display screen, even zoomed all the way in.


    If I don't take the leap and go for a dedicated astro camera, I'll probably be in the market for an upgraded DSLR.

    I read the comments to your post in the forum; all reasonable. But when budget is an issue (something that many posters don't seem to have a problem with and sort of ignore in their suggestions!) here would be my recommendations, with some explanation. 


    First, before you think about modifying your camera or getting a modified camera, read this  https://www.cloudyni...fied-dslr-r3276


    Having gone down the road of starting with a stock DSLR, then buying a modified one (both Canon T3i) then gone to a dedicated cooled CMOS OSC, my advice is stick with your stock camera for now, then decide if you  a) want to continue   B) want to stick with OSC or go the mono/filter/filterwheel route   (after looking at prices, processing requirements--mostly time and complexity--not that complex but finicky and more time consuming).  You will get great images and experience while figuring out where you want to go with this hobby, without spending money on something you then might want to turn around and sell to fund something else. Save time and money. 


    Not sure how you are acquiring your images--onto SD or connected to a computer directly? If you have a laptop already, you can use a number of good programs to great benefit. Both of my upcoming suggestions are only available for Windows, I think, but both work very well.


    If you use BackYardNikon, you can get a better focussing routine--fairly cheap (? $35 or so?) Getting longer exposures autoguided:  great idea, but if you are getting decent results unguided at 40 seconds to one minute, stick with that and upgrade elsewhere than autoguiding for the moment and spend your money on other stuff first.  


    An altenative to BYN that would probably work even better is NINA. Great package and free (well, I would suggest a voluntary donation--these guys are doing our community a huge service) I am not familiar with using NINA and a DSLR, but you should look at that for two reasons:  if it works, you can kill two birds with one stone. First would be using platesolving to get to your target--thought I had died and gone to heaven when I first tried it and in under a minute, I had my target centred in the field! the second reason:  autofocus.  Yes, you would need to get an autofocus device but then you would eliminate a major headache and get better results. 


    Autofocussers from ZWO and Pegasus work well; my experience with the ZWO EAF is good. Yes, the low price end ones have backlash, but NINA has no problem dealing with it. It doesn't make a difference in the end if you have zero backlash or 100 steps, since the software deals with it and you don't even notice it in the end. 


    On to autoguiding. If you are getting good results unguided at 40 seconds, I would try going a bit longer. One minute subs for many targets are fine. Autoguiding is great and necessary for many mounts going longer than 30 seconds and not horribly expensive, but if you can get good one minute results and wanted to make a choice between autoguiding and a cooled camera, I think I would go cooled camera first. Having said that, autoguiding is relatively inexpensive; hard one to call. 


    Anyway, lots to think about. Start with reading the Elf's article. He has a good website and started a great thread on processing practice as well (search Beginner imaging forum for  Nothing to Do? )


    Good luck!

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