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What should my next purchase be?


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So, as the title suggests, what should I buy next?

 

I'm starting to get more and more into the idea of pursuing astrophotography as a hobby.  I've taken a couple of roughly 20 minute integration photos, and am waiting for some more clear skies to take some more.  I currently have a 70D and an 80D, an 85mm f/1.8 lens, and an old 135mm m42 f/2.8 lens.  I'm using a Star Adventurer tracker, on an old telescope tripod that I converted to accept the star adventurer mount.

So now I don't know what piece of equipment my next purchase should be.  I'm mostly interested in Deep Sky at the moment, but may want to have a go at planetary in the future.

 

Here is the shortlist of what I've thought about.

1.  A 200mm f/2.8 lens.

2. A CLS filter for the camera(s)  (I live in a Bortle5 area)

3. Guide camera & scope.

4. Astro mod the 70D.

5. An actual scope & flattener (Something along the lines of a Sharpstar 61EDPH, or a similar price range)

 

I know that I'm the only one who can ultimately decide what I should get, but I guess what I'm actually asking, is what piece of equipment will give me the biggest boost to what I can photograph?

 

My current thought process is that the CLS filter would be the best place to start, since a couple of the targets that I'm interested in frame well with the lens options that I currently have available, so that bumps it above the new lens.  The Scope should probably come AFTER I have a Guider, since it's longer focal length will highlight the errors in tracking a lot more than the short focal length camera lenses.  The Guide camera and Guide scope should probably be pretty high options on the list also I would imagine.

 

Anyway, I just wanted to get some people's thoughts/opinions on the matter.

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The Star Adventurer will serve you well with a DSLR and short lenses, many award-winning shots have been taken with this setup. But sooner or later you will want longer focal length and more resolution which will involve a scope. Scopes are better corrected compared to camera lenses for the application in hand assuming you have the field flattener or coma corrector. 

At this point you have to consider weight and portability, because for astrophotography the starting point is the mount. Is it going to be used just at home, or set up regularly in some farmer's field? You need to add up the weight of all the kit you're likely to want including an OTA, camera, filter wheel, guidescope et cetera. A popular starting point for deep sky is an 80mm ED refractor (typically 4.5 kg with rings and field flattener) DSLR (700g), guidescope (500g) guide camera (300g) so you're looking at 6kg for a OSC rig, 7kg with a filter wheel for mono. For a beginner I's stick to one-shot-colour (OSC) but this is a contraversial point.

You mention planetary; I have seen good results with 80mm scopes but something larger with a bit more resolution will be more satisfying. 

If you're serious about AP then the HEQ5 mount is about the minimum that will allow you to carry this sort of weight and get consistent results bearing in mind that the practical limit for most mounts is about 1/2 to 2/3 of the visual weight. If portability is not an issue then something in the EQ6 class will keep you going for years with a wide variety of scopes and accessories. You can get results with an EQ3 or basic EQ5 but you may well find the percentage of successful subs is low. Given the UK weather it's worthwhile having decent kit just to maximise your use of clear nights. 

The mount will need to be capable of guiding corrections in both axes, usually via a ST4 port or pulse guiding. Full goto is not strictly necessary but makes finding objects a lot easier. Sometimes just getting a small faint target on to the camera chip can be a real chore. 

After the mount is sorted you will very probably want to sort out the guiding for longer deep-sky subs. Not so important for planetary lucky imaging. 

In most UK locations a filter is very beneficial. There are special clip-in filters to suit Canons but you will need to get another one if/when you trade up to a cooled astro camera. Secondhand Canon filters go for less than £100.

You're asking the right questions. A lot of people (including myself) start out buying any old cheap equatorial mount, scope and camera as and when bargains become available and regretting it because the setup was not planned as a whole!

Edited by rl
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I would suggest your points of 1,3 and 4. Getting a telescope requires a mount and that would be more expensive than anything else you planned for. Starting out with an EQ5 is the cheapest you can make work with many small setups, but ideally an HEQ5 to have some room for growth.

Drop the CLS filter as its sort of useless. Go full narrowband with a dual band filter like the optolong L-extreme or no filter at all. A CLS filter or similar will block a lot of light pollution and also with it lots of actual broadband light from the target so they are not suitable for broadband targets (like galaxies, reflection nebulae, dust clouds, star clusters etc). Narrowband filters block basically all light pollution but only let pass light emitted from emission nebulae. Skies are full of emission nebulae so this is the best bet, but note that this is also unsuitable for broadband. For broadband there are no filters for the job that make light pollution disappear without downsides. Darker skies or more total exposure are the only remedies.

The 3rd point, guider is very important. Since youre planning on still using very low focal lengths you can get a small guider + guidecam setup working for not that much money if you have a laptop you can use in the field. If not, youll have to get one, or a mini pc setup of some kind.

Your 5th point would allow you to do the most, but to be comfortable you would need a mount. Going that route youre looking for a cost of probably at least 2000 euros unless buying used. If you buy a cheap mount youre looking at a price of the cheap mount + the better mount when you get frustrated with it and upgrade and not end up saving money. 

If you dont want to be comfortable or have room for upgrades, the 61edph will probably run fine on the star adventurer, but personally i wouldnt want to do that as you still just have a manual tracker without Go-to capability.

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24 minutes ago, rl said:

Full goto is not strictly necessary but makes finding objects a lot easier. Sometimes just getting a small faint target on to the camera chip can be a real chore. 

I noticed this when I was able to image the LMC a few nights ago for half an hour.  (Had clear skies for maybe an hour and a half, but took an hour to get the rig set up and aligned.

Seeing as I'm in Australia, and have to pole star, and the Octans alignment stars are a PITA to find in the pole scope on the Star Adventurer, I wound up getting the 3 point polar alignment in NINA to work, and got to within a couple of minutes of alignment.

Since I already had NINA open, and plate solving was working well, I actually used that to frame the shot, just adjusting the RA untill I was on, then the DEC.  I shouldn't be surprised, but was blown away by just how accurately the LMC was centred in the frame.  The only thing I want to try next time I can see stars, even if not well enough to image, is to see if NINA can platesolve the 80D's webcam stream.  If it can, then I don't have to worry about 100 shots to the shutter count every time I'm aligning, or framing.

 

 

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It's a bit off topic but anything you can do to make things easier is time/money well spent. The learning curve can be very steep. Just practising with the kit in daytime can be helpful so that all the software fires up and talks to the hardware on cue.

Edited by rl
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OK, so it seems that I'm leaning very hard toward a guiding setup.  I figure that one of the cheap 30mm scopes would be more than adequate, is there much of a difference between a colour and a mono guide camera?

I figure this would also make my setup, and framing a lot quicker too.  I believe that setup should be a little quicker at least now that the alt on my mount is set, and should be close depending on how well I can level the tripod.

 

I don't plan on buying too much stuff that won't serve me in the long run.  About the only reason that I justified the Star Adventurer over a proper GOTO mount, is that even when I have a proper mount, I can still use the Adventurer for portable use if I ever want to go on a camping trip.  Eventually, I think that when I'm ready for a proper mount, I'll go for something like an EQ6-R, or equivalent.

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30mm will do. 50mm goes fainter..

In theory a mono guide camera will see fainter stars but in practise most people don't see much difference. And a colour guide cam can make a good planetary camera. Choosing one with a good frame rate and a frame buffer can stop USB lockup issues when doing lucky imaging.

A lot of 30/50mm finders can be adapted to take a guidecam. There is an adapter for this. 

Edited by rl
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23 minutes ago, rl said:

30mm will do. 50mm goes fainter..

In theory a mono guide camera will see fainter stars but in practise most people don't see much difference. And a colour guide cam can make a good planetary camera. Choosing one with a good frame rate and a frame buffer can stop USB lockup issues when doing lucky imaging.

A lot of 30/50mm finders can be adapted to take a guidecam. There is an adapter for this. 

So would something like the ASI120MC would be a good choice, coupled with a  30mm scope at 130mm focal length?

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I use an ASI120MC very successfully. The MC-S version supports higher frame rate over USB3 useful for planetary but not essential for guiding; pointless if the PC can't keep up.

GPCAM2 is another good choice, as is QHY5_2. And all have the ST4 guide port which connects to the mount delivering the corrections.

30mm at 130mm FL should be ok. 50mm at 200mm will theoretically see and correct smaller guide errors with fainter stars. Given the choice I'd go with 50mm but it's not a dealbreaker if you really need the more compact guide scope and your main scope is fairly short. 30mm certainly ok for camera lenses. 

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Thanks for your guidance.

 

I'm pretty sure that's the route I'll go.

I'm not too concerned about buying the 30mm scope, and then needing a 50 or larger eventually, as like the tracker, will still be useful for portable setups.

I know I should just wait for clear skies, and use what I have and get more experience before spending more money, but at the same time, the sooner I can get my list to Santa, the better my odds of getting it lol.

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