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I recently purchased my first telescope and camera, and now I want to make sure I have the correct Barlow or reducer to couple them together to achieve Nyquist sampling on the camera (or slight over-sampling). In case it’s important, I’m interested in planetary imaging—in theory that shouldn’t matter for this sampling question, but maybe there are other considerations to take into account.
I used this calculator (https://astronomy.tools/calculators/ccd_suitability) and plugged in my info:
Telescope: Celestron 8 SE
Camera: ZWO ASI462MC
Seeing: experimented with this one, but would like to get optics that allow for poor or very poor
Binning: prefer 1x1 to preserve spatial resolution, but could consider higher if SNR is a problem
I’ve seen on several forum posts that people often use a 2x Barlow to couple the two. However, according to this calculator, that will always lead to over-sampling. If anything, it says I should use no intermediate optics or even a reducer.
So my questions are:
Binning: Will I be able to see anything with 1x1 binning, or should I expect to need to bin to collect enough light?
Is there some other consideration that’s more important here than achieving correct sampling? It seems like most others are over-sampling, and perhaps there’s a good reason for this. If so, is there another formula that would let me determine the appropriate optics to buy?
Thanks in advance for any help!
Hi, i have made a video where i show a coople of eyepieces that i use and like, and also show how a barlow works, compared to the "Powermate" from Televue. And how is the FOV affected when changing the magnification with different eyepieces?
Feel free to comment and give me feedback - I hope you like the video!
I picked up a Celestron Omni last year quite cheaply and had originally been using that with stock eyepieces, which was fine.
Since then I've bought a couple of BST Starguiders and a Hyperflex zoom, and I'm now wondering if I'd notice any difference with a better barlow (this is now being used on an F/5 150mm Newtonian). Otherwise, the pennies can be directed elsewhere.
I'd not considered it before as the next rung up seemed to be around the £90-£100 mark, which seemed out of line with the rest of the spend. But I've seen some positive reviews of 3-element models in the region of £35-£40.
In particular, I've read good things about the Revelation/GSO Astro 2.5x (though apparently closer to 2.2x) and the Baader Classic Q 2.25x.
- does anyone have experience with both of these, and have a preference?
- would I notice any significant difference with either, compared with the Omni?
- I read somewhere that the Baader in particular required focussing the tube into the OTA to an extent that caused some image degradation. Obviously I'd want to avoid this if true, so is this a feature of the Baader, or of both, or of all (shorter?) barlows? (to be honest, I'd not thought to see whether this was happening with the Omni, I'll try to remember to check, if this weather ever breaks).
Thanks in advance.
My lovely wife bought me a SW Explorer 130 with the basic RA drive for my 40th birthday 8 years ago, and I've enjoyed using it on and off ever since. I've started getting more into it - it's a great beginner scope, but I'm - like lots of others on this forum - looking at upgrading. One of the things I found tricky with the scope was getting the focus just right at high magnification (I'm sure that's kind of obvious!). It does wobble quite a bit on the EQ2 mount when focusing. I get pretty good - if small - views of Jupiter, Saturn, (the Moon, of course) and have had hints of seeing some DSOs.
I bought a 8mm BST Starguider, and it's a great improvement on the standard 10mm that comes with the scope, but if I push the scope by adding the 2x Barlow and the 8mm it's a blur and the focus seems to keep missing the sweet spot. I saw a post elsewhere on this forum by MakTheNight, (looks like they've left now - last post was 2 years ago) who added a Baader Helical Focuser that attached directly to the T-thread on the focusing apparatus on the SW. Link to that post is below. I got one and it is indeed a great improvement on fine tuning - the problem is I can't use it with the Barlow as the helical focuser is about an inch long and the focuser can't move far enough into the scope to focus with the Barlow and any of my eyepieces (the 8mm BST, or the 10 or 25mm standard eyepieces)
Clearly MakTheNight managed to get their setup to work with some specific eyepieces (a Luminos 10mm and 32mm Plossl) and a specific Barlow, so I tried looking up how I could work out what combination of eyepieces and Barlow would work, rather than randomly buying kit and having to return it because it won't work with my scope, but I haven't found anything useful yet. So I thought I'd take the plunge and ask here
Can anyone help me figure out how I can calculate what combinations of eyepiece and Barlow would work with this setup? I'm also looking at upgrading the OTA and mount to a 200P and EQ5 at some point, so ideally would have a combination that could work with that too - the focal length and mirror is quite different - 1000mm on the 200P parabolic vs 900mm spherical on the 130.
Tonight I was looking at Jupiter and got some nice views with a range of eyepeices. The best image detail wise and for clarity of image was a 15mm, which on my 8" Evolution gives me appx 135X
I tried using my Televue 2X Barlow which normally works fine. I can't remember exactly which eyepiece this happened with, maybe the 15mm or a 9mm, but when I used the barlow the planetary image would soon disappear out of the eyepiece. The mount seemed to otherwise be tracking OK although notice the planets seem to move out of the eyepiece view after a while. So did I have too much magnification with the Barlow? I think I did manage to get focus, the image just wouldn't stay put.
Thanks for any insights or advice