advice on planetary imaging

[Dan13]

Morning, I have a dso set up but as per usual in this rabbit hole of a hobby im also looking to grab a fairly "cheap" planetary set up.

I already have a asi 224 so ideally would like to use that in conjunction with an 8" or 10" Dob. I had an XT8 dob a while back (that i now regret selling) but always struggled to image with it, could someone advise on the best extentions and materials needed to make my 224 work with an 8 or 10" dob for imaging mars this coming oct.

many thnaks

Dan 

[Cosmic Geoff]

I suggest you check the 'Planetary Imaging' section of the forum to see what gear others have been using.  It's not impossible to image with a Dob (and it's not impossible to cross the Atlantic in 🙂a rowboat. )  But the best tool for the job is a SCT of aperture 8" or greater.  The depth of focus makes it easy to attach imaging accessories - cameras, atmospheric dispersion corrector, flip mirror, filters.  As for the mount, either an alt-azimuth or a equatorial mount will serve, but it makes the task a lot easier if the mount is rigid, tracks, and has a minimum of backlash.  Without accurate tracking, a planet will go out of  a 320x240 pixel ROI very quickly.  The CPC800, for instance ticks all the boxes with its substantial fork mount, mimimum backlash, and GoTo but unless you get a great second-hand deal may cost more than you want to spend.   I also tried using a C8 on a EQ-5 Pro Synscan mount, but by comparison with the CPC800, the amount of backlash was quite annoying, and the potential for a 'meridian flip' when working near meridian transit equally annoying.

And you need a good finderscope - just getting a planet onto a small camera chip is a challenge in itself.

[Dan13]

24 minutes ago, Cosmic Geoff said:

I suggest you check the 'Planetary Imaging' section of the forum to see what gear others have been using.  It's not impossible to image with a Dob (and it's not impossible to cross the Atlantic in 🙂a rowboat. )  But the best tool for the job is a SCT of aperture 8" or greater.  The depth of focus makes it easy to attach imaging accessories - cameras, atmospheric dispersion corrector, flip mirror, filters.  As for the mount, either an alt-azimuth or a equatorial mount will serve, but it makes the task a lot easier if the mount is rigid, tracks, and has a minimum of backlash.  Without accurate tracking, a planet will go out of  a 320x240 pixel ROI very quickly.  The CPC800, for instance ticks all the boxes with its substantial fork mount, mimimum backlash, and GoTo but unless you get a great second-hand deal may cost more than you want to spend.   I also tried using a C8 on a EQ-5 Pro Synscan mount, but by comparison with the CPC800, the amount of backlash was quite annoying, and the potential for a 'meridian flip' when working near meridian transit equally annoying.

And you need a good finderscope - just getting a planet onto a small camera chip is a challenge in itself.

Thank you Geoff, some useful info appreciate it. I have a 50mm guide scope i could use for my finder and i was hoping to use my HEQ5 for the tracking, im wandering if a larger PDS would be the better way to go tbh ?

[CraigT82]

If you already have a heq5 why would you want to get a dob? Just plonk an 8" tube on there and you'll be fine. A C8 would be good but also consider a mak or an 8" newt. 

[Dan13]

2 hours ago, CraigT82 said:

If you already have a heq5 why would you want to get a dob? Just plonk an 8" tube on there and you'll be fine. A C8 would be good but also consider a mak or an 8" newt. 

the dob was more due to not having to keep taking my frac off the mount but the more I think of it a tube def seems the better option. Is the 200pds any good? I had the 130 and it was great so image the 200 should give a lot my FL for planetary but keep the imaging situation well 

[CraigT82]

Oh I see... well plenty of people do get great planetary images with a dob, though I'd suggest budgeting for an equatorial platform if you go down that route.

A 200pds would be fine, 8" aperture is enough to get some real detail, couple it with a decent 3x or 4x focal extender and you should be able to get some nice images. 

Whatever you do, I'd think about getting an ADC too, money well spent in my opinion! 

[Dan13]

1 hour ago, CraigT82 said:

Oh I see... well plenty of people do get great planetary images with a dob, though I'd suggest budgeting for an equatorial platform if you go down that route.

A 200pds would be fine, 8" aperture is enough to get some real detail, couple it with a decent 3x or 4x focal extender and you should be able to get some nice images. 

Whatever you do, I'd think about getting an ADC too, money well spent in my opinion! 

Great thanks Craig, appreciate it mate

[Cosmic Geoff]

You may have trouble getting an ADC to work with a PDS Newtonian, as it adds several centimetres to the light path.  Which is why I suggested using a SCT.   I got a  used C8 + SE mount for £650.  You might get an OTA for even less.

[CraigT82]

11 minutes ago, Cosmic Geoff said:

You may have trouble getting an ADC to work with a PDS Newtonian, as it adds several centimetres to the light path

Yeah that is true. Using a barlow should kick the focal point out far enough though. 

[nfotis]

On 02/07/2020 at 12:52, Dan13 said:

Thank you Geoff, some useful info appreciate it. I have a 50mm guide scope i could use for my finder and i was hoping to use my HEQ5 for the tracking, im wandering if a larger PDS would be the better way to go tbh ?

 

If you have already a HEQ5, you should consider a Skymax 150 or even a 180 for planetary imaging, I think.

 

N.F.

 

[knobby]

Or better still a used C9.25 ... As for getting a planet on a small chip, make sure finder is aligned as well as possible to camera, defocus the scope a bit and ramp up the gain, it's much easier finding a big bright donut than a tiny planet.

[Dan13]

18 hours ago, nfotis said:

 

If you have already a HEQ5, you should consider a Skymax 150 or even a 180 for planetary imaging, I think.

 

N.F.

 

Thank you I'll take a look. I was looking at some cheap 200p's yesterday as I already own a 2 and 3x Barlow 

[Dan13]

17 hours ago, knobby said:

Or better still a used C9.25 ... As for getting a planet on a small chip, make sure finder is aligned as well as possible to camera, defocus the scope a bit and ramp up the gain, it's much easier finding a big bright donut than a tiny planet.

Thank you 

[PeterCPC]

A flip mirror helps as well.

Peter