Lens upgrade suggestions.

Hi,

I stumbled with an EF 300 f/4 L on a Bresser Exos1 mount into astro photography. I think, the 300mm range is quite good. But the problem is, that every lens that is made for standard photography is basically a compromise between sharpness and contrast with the focus set to infinity. The stars will usually have some fringes and are less sharp at the edges of the frame. But there are some sharp primes with better values that you can get within your price range. But they will also be a compomise.

If you like to get into that astro stuff, have a look at the askar lenses. They are made especially for astro and you may get better values at infinity. They have a 180mm lens (FMA180) and a 135mm lens (FMA135) that are quite affordable. I never used one of those, but heard a lot of good things about them (but not exclusively). The star adventurer should handle those lenses really well.

That is just my suggestion and the the way I would go. But I am sure, that there are some other opinions here.

CS

Christian

I’m currently using a Canon 2000D with a 75-300mm telephoto lens on my Star Adventurer 2i, what would be a good lens upgrade for a beginner like me that will yield much better results than my 75-300. (trying not to go over $550 but can make exceptions).

Canon 200mm f2.8, insane sharpness, check my gallery as I mainly use one.
CS
Axel

so I haven’t uploaded images because I can’t get my stuff to properly work (stacking and editing) I just need someone to physical guide me. My photos keep coming out with quite a bit of noise as well. I was using the cam at 300mm 1min exposure and iso 1600. My star tracker worked great but the images said no. I think it might have been my light pollution filter to be honest. As to why I have an adjustable 75-300 is that I have it for regular photography and learned that it can be used for Astrophotography (to an extent ). I do not need a variable length (while it would be nice but it’s gonna cost more so at the moment no) I’m looking for set focal point that will provide sharp images for Astrophotography for under $550, I want to be able to capture all sorts of objects and why not. I’m looking for a focal point really above 130mm.

I also started with a similar setup. Getting the right focus was really crucial. It took me about 10 to 15 minutes with manual control to set it to the right point. I used Astro Photography Tool at that time, which helped me to get the HFR or FWHM values. At that time, there were not auto focus routines on those software tools. That has changed now and APT as well as Nina or other ones have solutions, to use the motors of the lenses and run auto focus cycles. It is much easier now.

With a focal length of 300mm and your APS-C sensor, you should keep the exposure time at 120s or below. At least in my case, everything above starts to get blurry. With guiding, that would change a bit, but that is the next step. Depending on the light pollution in your region, you have to take a lot of frames to get rid of the noise. I suggest at least 2 hours of data. There always will be some noise left in the frame, but usually it is managable.

Things got better for me, as I started to take calibration frames (bias, flats and darks). While bias and flats are quite easy to take, the darks made some problems. During nights, where the temperature falls very fast, I took 2 lights and after those I took 1 dark. If the temperature is quite stable, you can expand the cycles to 45/15 minutes. I guess, other users have their own opinion about that ratio. But in the end, I used Deep Sky Stacker to get the final image.

Here are my first succesful images with this setup. It took me not so long to reach that point.

https://www.astrobin.com/ozkn6q/

https://www.astrobin.com/t1o4cp/

https://www.astrobin.com/2b6fyp/

I think, that the lens you use is at this point not your problem. It will work and at least in the image center, everything should look ok. With your APS-C sensor, the edges can't get too bad, because the lens is made for full frame.

I'd like to challenge you to keep getting better. The first tries are hard. But if you are succesful, it was worth it. Just keep trying!!!

Hope this helps

Christian

Björn Arnold:
…

so I haven’t uploaded images because I can’t get my stuff to properly work (stacking and editing) I just need someone to physical guide me. My photos keep coming out with quite a bit of noise as well. I was using the cam at 300mm 1min exposure and iso 1600. My star tracker worked great but the images said no. I think it might have been my light pollution filter to be honest. As to why I have an adjustable 75-300 is that I have it for regular photography and learned that it can be used for Astrophotography (to an extent ). I do not need a variable length (while it would be nice but it’s gonna cost more so at the moment no) I’m looking for set focal point that will provide sharp images for Astrophotography for under $550, I want to be able to capture all sorts of objects and why not. I’m looking for a focal point really above 130mm.

Hi,

when you say your issue is stacking and editing then a new lens won’t change the game. Of course, I implied that you have good raw material. That said, I strongly recommend against buying a new lens right now and first nail down where the issue is.

So, here would be my suggestions:
1. Make sure you get your sky tracker dialed in, i.e. you should have round stars in the center of the field under longer exposures.
2. Start with bright targets like M31 or the Plejades which are about to come up nicely.
3. Don’t use the light pollution filter in the beginning. Do it step by step.
4. (Some) Noise will be there. The question is only to which extend. Dialing your camera in is one thing. The other is noise reduction during post-processing.

This list can be easily extended but my point is: analyze the process and identify the major issues. I bet the lens isn’t among the top three.

Also feel free to share data so others can take a look. No serious person will criticize it but will try to be helpful.

Cheers,
Björn

I support Elmiko point. 
Within your budget, if 135mm is good and enough for your purposes, Samyang/Rokinon 135 f/2.0 will be honest choices. It's really decent lens: fast & sharp. SA tracker also give you possibility of longer subexposures on such focus length.

You also can try Canon 70-200 IS UMS  f/4.0 for 200mm.