I’ve been trying to sell my Celestron 80mm refractor for a while now but haven’t had much luck. The reason for selling is the tube itself is quite heavy for my setup and opted for something else.
I was wondering would I be able to use it to image the Moon and do some wide field DSO since it has a low focal length or is it purely just designed for guiding?
Bit of a silly question but wanted to ask if I can use it for some imaging or are the optics going to make it impossible? Is it just a normal refractor but re-boxed and sold as a guide scope?
It's a normal refractor but the CA would kill it You might need extension tubes as well. i had the Orion version and it was ok for looking and imaging the moon with a mono camera
It's a normal refractor but the CA would kill it You might need extension tubes as well. i had the Orion version and it was ok for looking and imaging the moon with a mono camera
Would there be any way to reduce the CA?
I've been reading that the tube is an achromatic which I am assuming helps with the CA?
Last edited by 04Stefan07; 02-04-2018 at 07:52 PM.
The problem noted above is most pertinent for OSC, because you get chromatic aberration at any single focal point. In theory, you can do LRGB imaging, provided you re-focus for each filter change. In practice, achromats tend to induce bloated stars on the blue channel regardless. They are fine for narrowband, as the bloating is minimized.
I speak from experience, imaging with a SW120 achro. There are a few images in my Astrobin (see sig) that show this for some emission and planetary nebulae.
You can use a yellow filter or a light pollution filter which will reduce the effects a bit, but CA is worst on short focal length achromatic scopes, Baader also make some specialty filters for this purpose.
The CA is not to bad if you have no bright stars in the field of view though, M31 no filter 120mm f5 achro, and sometimes it works really well, January's lunar eclipse.
Here's an example of the Orion nebula with a light pollution filter, 120mm f5 achro refractor.
Achromatic scopes with a longer focal length can counter CA but the celestron is a short focal length, there are filters that cut out some of the violet colours
That's a big difference with the light pollution filter!
Which filter are you using?
Quote:
Originally Posted by doppler
You can use a yellow filter or a light pollution filter which will reduce the effects a bit, but CA is worst on short focal length achromatic scopes, Baader also make some specialty filters for this purpose.
The CA is not to bad if you have no bright stars in the field of view though, M31 no filter 120mm f5 achro, and sometimes it works really well, January's lunar eclipse.
Here's an example of the Orion nebula with a light pollution filter, 120mm f5 achro refractor.
Stefan i have been watching you try to sell that Celestron 80mm guidescope, as i have one in storage myself. I really bought it to get the ring set and DVR clamps that it comes with which individually are worth more than the scope. One possible use you could consider is narrowband imaging. I used to image with a Bresser achromat scope and it was a very cost effective capable narrowband scope. Narrowband will allow you to escape the CA issue. You will need to check focus for each filter, but once you register the subs, alignment will be fine. I used to run my NB subs through DSS, obviously one stack per filter, but then re-registering the output Tiffs for each filter to align them for final processing. Its doable, and since your in Melbourne, narrowband might get you more use than RGB.
Stefan i have been watching you try to sell that Celestron 80mm guidescope, as i have one in storage myself. I really bought it to get the ring set and DVR clamps that it comes with which individually are worth more than the scope. One possible use you could consider is narrowband imaging. I used to image with a Bresser achromat scope and it was a very cost effective capable narrowband scope. Narrowband will allow you to escape the CA issue. You will need to check focus for each filter, but once you register the subs, alignment will be fine. I used to run my NB subs through DSS, obviously one stack per filter, but then re-registering the output Tiffs for each filter to align them for final processing. Its doable, and since your in Melbourne, narrowband might get you more use than RGB.
Hey Glen,
Yep I am convinced in keeping it and using it for some sort of imaging. Surprised it didn't sell. I initially bought it as a guidescope for my SCT 8" but the tube and accessories were so bloody heavy!
Since you have one, do you know the diameter of the scope because I want to get some tube rings for them. Maybe 90mm tube rings?
Yep I am convinced in keeping it and using it for some sort of imaging. Surprised it didn't sell. I initially bought it as a guidescope for my SCT 8" but the tube and accessories were so bloody heavy!
Since you have one, do you know the diameter of the scope because I want to get some tube rings for them. Maybe 90mm tube rings?
How did you buy it without the rings and clamps? Mine came as a completed set from Bintel (on sale) and i suspect they were running out the product. As i said before, the value for me was in getting the rings and clamps as part of the deal. I will check the rings and get back to you.
The rings that came with my 80mm guidescope are 125mm ID, and the clamps are for the 3" wide Losmandy/ CGE style bars. Celestron product number for the ring and clamp kit is: #93786.
Good luck.
Maybe smaller rings would work, you can measure your scope at the big end to size the rings you need.
If you want to use proper tube clamp type rings ( without the screws) then again you can measure your tube. You can always pad thise rings with felt if they are alittle too big.
How did you buy it without the rings and clamps? Mine came as a completed set from Bintel (on sale) and i suspect they were running out the product. As i said before, the value for me was in getting the rings and clamps as part of the deal. I will check the rings and get back to you.
Nah mine came with the complete pack, I just sold off the rings but I still got the clamps.
The rings that came with my 80mm guidescope are 125mm ID, and the clamps are for the 3" wide Losmandy/ CGE style bars. Celestron product number for the ring and clamp kit is: #93786.
Good luck.
Maybe smaller rings would work, you can measure your scope at the big end to size the rings you need.
If you want to use proper tube clamp type rings ( without the screws) then again you can measure your tube. You can always pad thise rings with felt if they are alittle too big.
Thanks for that information!
I will have a look into getting some filters to help with CA and make sure they are compatible with my 1200D and 1.25" cameras.
Hi all. I read once that using a Minus-violet filter was the go to reduce CA. It work well for visual use but I don't know how it would go for imaging.
Cheers!
I've tried many filters to help with CA. The most effective of the lot was a cheap hoya K-2 yellow filter. It even beat the 20x more expensive Baader semi-apo filter. Just correct for colour balance in processing.
