What to upgrade / refractor vs telephoto?

[DrummerSP 5]

Hi!

Firstly apologies if this is in the wrong section (this is my first post on any kind of forum!) and I'm aware its a question thats probably been asked thousands of times. Please let me know if I should post elsewhere or anything...

So I've made some progress with astrophotography but as much as I try I get so confused with lenses and the specifics so thought I'd ask people who understand them more. My setup so far is a Canon EOS 550d, with a 70-300mm f4-5.6 lens all on a Star Adventurer pro tracker (recently upgraded from an Omegon LX3 mini track). The camera and lens were both second hand and passed down to me so I dont really know how old they are now but I've been getting good results so far (uploaded one of my recent images, still using the minitrack for reference)

Basically I dont know if I'm better off upgrading the camera and sticking with the telephoto lens (from what I can find its a good lens), or would changing to a small telescope be better. If I was to, from what I've found the Sharpstar 61EDPH II would be a good choice?

I've researched a lot and just dont understand the technical side enough to know where I'm better off putting my money. My budget would be around £1000, maybe slightly more for a camera as I do use it for other photography too. Any advice would be very appreciated, sorry for the long post!

[vlaiv 5,652]

Hi and welcome to SGL.

As far as astrophotography is concerned - I think you are better of getting a small telescope rather than changing to another camera. There are couple of reasons for that:

- there won't be much difference in results you are getting with different camera unless it is either modded for astronomical use (changed IR filters and such) or is dedicated astronomy camera. Either of the two won't suit you since you use your camera for daytime photography.

- Although this lens is good by photography standards - it simply can't compete with a telescope - even a small one. Lens are not diffraction limited - they don't need to be in order to be sharp enough for their intended use. Telescopes on the other hand are considered just "good enough" if they are diffraction limited - and we in general value even sharper views from telescopes.

Being diffraction limited is technical term - you don't have to worry about it now - it just tells how sharp/magnified image can be - lens don't provide enough sharpness for astro images unless you take special care.

To emphasize what I mean - here is crop from your image - notice size of stars:

And here is same target captured with 66mm telescope:

As you can see - size of the target is fairly similar - this was taken at ~ 250mm FL, but I think that difference in sharpness is obvious.

I think that SharpStar 61EDPH is very good choice as replacement for your lens. It is of similar focal length that you are used to with this lens - and it is of similar speed at about F/5.5 (or even F/4.5 with reducer).

[wxsatuser 5,527]

You can get better images with a lens but the cost comes near to mid to high end scopes.

As above, a small refractor should be fine and for your budget get a more modern camera as well.
Look around MPB should find something nice for £600.

[DrummerSP 5]

Thank you both for the replies and all the info thats helped a lot. 

I can definitely see the difference in the example you shared and im definitely leaning more to the sharpstar now I think. This image is slightly better i think with the same equipment but not sure the focus matches your example still...

Although I have been suggested this astrophotography dedicated lens... (Askar 200mm) https://www.firstlightoptics.com/askar-telescopes/askar-acl-200mm-f4-apo-camera-lens.html which is now adding another option...

Would the sharpstar still be the better choice over that lens? I wish I understood the types of lenses better but its a lot to take in so really appreciate the help! 

I'll definitely have a look on MPB and see what cameras are available too thank you.

[vlaiv 5,652]

56 minutes ago, DrummerSP said:

Thank you both for the replies and all the info thats helped a lot. 

I can definitely see the difference in the example you shared and im definitely leaning more to the sharpstar now I think. This image is slightly better i think with the same equipment but not sure the focus matches your example still...

Although I have been suggested this astrophotography dedicated lens... (Askar 200mm) https://www.firstlightoptics.com/askar-telescopes/askar-acl-200mm-f4-apo-camera-lens.html which is now adding another option...

Would the sharpstar still be the better choice over that lens? I wish I understood the types of lenses better but its a lot to take in so really appreciate the help! 

Yes, that image has much better resolution. You can quickly compare resolution of two images - if you can spot stars in the image that are close but have been resolved as separate stars (that is what resolution is all about - actually resolving detail).

Difference between telescope and a lens is in number of elements as well.

Telescopes have 2-3 glass elements in front lens (assuming they are refractors), while photographic lens can have dozen or so elements. This is because telescopes are optimized for objects at infinity, while photo lens should offer good performance for both far and near objects. As such - they are often not well optimized for infinity focus in the same way telescopes are.

As for lens that you linked, well, I'm biased, and I would prefer 60mm scope that you can use at F/6 or turn into F/4.5 with addition of reducer than 50mm F/4 lens. This is simply because I love scopes

Something like this for example:

https://www.teleskop-express.de/shop/product_info.php/info/p10095_TS-Optics-PhotoLine-60-mm-f-6-FPL53-Apo---2--R-P-Focuser---RED-Line.html

Then again - I see them as scopes - versatile instruments for observing universe. Don't want to image on particular night? You can just observe instead. You can't do that with a lens.

Lens like that Askar has it's strengths as well - no need to fiddle with adapters and connections and spacing - just attach camera and you are ready to go. Once you start using dedicated astro cameras things shift in favor of telescopes again. It is easier to connect dedicated astro camera to telescope than it is to lens.

55mm of flange focal distance or less - does not leave you enough space for all the things that you might need like - rotator, filter wheel, adapters, OAG and such ...

 

[DrummerSP 5]

Thanks again for all the information!

That makes sense that a telescope would do a better job at infinity as they are designed for that purpose where lenses are for near and far.

Another good point about being able to observe and not just image... I'd love to observe as well so this would be a plus, however my main goal is to get quality images so my initial thought was to focus on imaging first. But even having some observation, even if the scope was more for imaging would be a fun addition.

I do like the portability and lack of attachments/fiddling with adapters etc that lenses offer. Its a lot more like connect and shoot instead which definitely suits me better. Also the ability to do landscape astro with a lense too.

Maybe having the canon f4L lens is more than good enough for now and will work for travelling/setting up quickly and a small refractor in the future for set up at home with more time and even some observing. Having both would solve the decision 

[rickwayne 384]

If you do decide to stick with camera lenses, you will probably get better results from fixed-focal-length (prime) lenses than zooms. Optical design is a game of compromises, and the more complex the design, the more likely it is to compromise something you wanted.

Autofocus does you no good in astro, so a manual-focus lens is fine. Auto-exposure, same same. So you can actually look for quite old lenses in the used market, and they don't even have to be Canon brand. (They absolutely should be multicoated, though.) For example an M42 adapter that lets you reach infinity focus opens up a whole world of Pentax and other old, good glass. You should be able to pick up, say, a Pentax 300mm f/4 for under £120.

[Ande 235]

Before you do buy a telescope, it just might be worth having a peep at this thread: 

 A lot of people are achieving stunning results with this lens. Not me, I’m useless. But just about everyone else

[DrummerSP 5]

I only recently looked into the differences between prime lenses after seeing them mentioned so often. I have a zoom at the moment so thats definitely something to consider... I normally focus and forget that the focus changes when I zoom so it would stop that too

Wow those are some amazing pictures using that lens! I'll definitely look into that one before I make a decision... So many choices and options but thanks for everyone's help/advice!