cheap vivitar 500mm F8 lens. any astrophotography at all?

[realflow100]

I think I got a "lottery" model.
There is pretty good image sharpness all across the frame.
Theres some CA but thats to be expected (Not bothered by it much. I can remove almost all of it in processing anyways with the new techniques I discovered)
The only issue I can really see is being an F8 lens. so full 30 second exposures at a high enough iso are needed to get any kind of stuff visible.

Is there any tips I could get for maximizing the use of it? I have a canon 500D camera to use with the lens.

Compared to my 55-250 IS II lens the image quality is almost just about the same.

its Way extremely better than my F5.1 70mm refractor telescope so much sharper all across the image frame.
Even sharper than my F4 100mm reflector telescope

Am I limited to just planets and some stars? or is there any deep space object targets that could work?

heres a test image at F8 with a low iso

[Sandy04]

I'm assuming this is a mirror lens.

I had a 1000mm Russian MTO which gave beautiful CA-free images, but at F10, was too slow for DSOs.

Once I swapped my DSLR to a mirrorless body, I could fit a speed booster in the imaging train and took it from F10 to 710mm and F7.1. I sold it a while back, but kind of miss it now!

[realflow100]

Nope its a refractor lens. not a mirror lens.
It might be possible to make some kind of adapter to make a speed booster work with it (a mild speedbooster)
because it has a long extension piece screwed on before the rear lens element. so theres plenty of room for a speed booster and moving it closer to the sensor.
but its not a mirror lens. its just a 4 element refractor based lens. seems the rear element pair acts as a sorta barlow group adding to the focal length. and corrects some of the optics.

[SkyHiker]

At 500 mm in fact you should get a motorized tracking mount on a tripod. Add a remote timer for bulb mode and you should be in business with a beginner setup. If you went with the 250 mm IS lens a DIY barndoor tracker may be able to handle it if it is well made.

[realflow100]

I have a motorized alt az tracker already. but its got some kind of issues where it causes trailing up and to the side slightly (no matter where in the sky I aim it.)
ive tried setting it up as perfect as I can like a dozen times and it just doesnt matter what I do. its always got tracking problems if I expose longer than like 10 seconds at 500mm.
if I try a whole 2 minutes to try to see whats happening the trailing is really severe.

Should I do a really long exposure and post it to see if anyone can help me figure out why its trailing so much? while tracking a known star or something?

it also doesnt matter how the weight is balanced on it either. back heavy or front heavy. or perfectly balanced in the middle. it just doesnt make any difference. same trailing either way.

I have a 55-250mm IS II lens but it has a sharpness issue. (image is pretty soft and low contrast for some reason since a few weeks ago)
cause if i wiggle the focus ring around i see stars shift and slightly look like seagulls or comets. even in the center of the image. its like the front element has too much slop in the focusing mechanism and so it causes stars to look weird.

[SkyHiker]

That iOptron cube? For that, the AP the limit is probably about 10 seconds. So if you don't mind stacking a bit more, try it. M42 is very bright, try 30 x 10 seconds and you should get something.

[realflow100]

I have done that before.
I got about 13 frames of orion at 20 seconds with a 360mm refractor telescope (it was not very good quality though. pretty bad)


I'm going to need at least a few hundred frames if I want to get any faint details. and sharper stars
but the problem is i have so much light pollution that stacking and aligning stars doesnt work very well. Too many hot pixels show up. and theres not enough stars to stack with. so its hit or miss if the program cares to stack the frames or not.
sometimes it just gives up and doesnt stack anything.

[realflow100]

oops fail in the original post. image was downscaled for some reason

heres a 100% crop of the original not downscaled