You really need to define inexpensive.....
Film Camera
Let's say you score an old film body with a 135mm lens on the cheap - for free along with a tripod (thus no out of pocket capital costs). Then there is the reoccurring cost of film, development and digital scanning.
- Color film - buy for $10 roll (36 frames), $5 for development (with scanning)
- Black & White film - buy for $10 roll (36 frames) and you develop it yourself and scan it yourself (say buy a scanner for $100). But to get color images,you need to shoot 3 to 4 frames (with different color filters) and then stack them digitally (keeping track of which frame used what color filter)
Now, when you are shooting the frames, you need to shoot 8 to 16 frames per object and stack them in order to capture sufficient light so that they start to actually show up. Just for the ease of the numbers.
- Color film - 1 roll per object so $15 per shooting the sky object.
- B&W film - 3 rolls per object (RBG color filters), with you doing the developing and scanning, so about $30 per object (plus chemicals).
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Digital Camera
Using the lens and tripod you scored with the film camera for free - you will need to buy a digital camera potentially with a GPS tracker to extend the duration of your exposures. Let's use a K70 (you can find them for ~$450) and a O-GPS1 (~$120), which totals about $570. To really get longer exposures for deep sky objects, you will need an equatorial tracker like an ioptron (runs about $500+).
A friend shoots astro (Milky Way over landscapes) with a K70, O-GPS1 using a Sigma 18-35/f1.8, using a tripod and head. (an Rokinon 16mm/f2 is less). Here is his InstaGram page -
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When compared to film - looking for the break even point ....
- Color film - $570 / $15 roll (per sky object) = 38 sky objects with color film
- B&W film - $570 / $30 roll (remember you need RGB color frames) = 19 sky objects with B&W film (doing your own development and buying a scanner)
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If this is going to be an ongoing interest of your, digital is the way to go, which is going to require some up front capital costs. This also pre-supposes that you use free post processing utilities, like GIMP, etc.
Take a look at this area here on the Forum --
https://www.pentaxforums.com/forums/groups/135-astrophotography/
One of the favorite bodies for deep space objects is the K5 (~$150 used) on an equatorial tracker (~$500) with a 200mm to 400mm lens. [Note - the difference is with star color. If you are going to shoot deep sky objects, you are going to take many frames and stack them for the color, thus a K5 works very well (especially at ISO80. For the Milky Way over stuff, the K70 work better since you get immediate star color and really only need to shoot a 70 second sky frame using the O-GPS1 for tracking. Just my opinion]
Last edited by interested_observer; 12-23-2020 at 03:02 PM.