Jupiter + GRS with DSLR 22/04/2017

[Tommohawk]

Hi all.

Well the weather forecasts were all totally wrong - they all said cloud and I got lots of lovely sun in the afternoon and a nice clear sky 'til 1a.m. Fabulous.

Seeing was a bit iffy as GRS hove into view but fortunately settled nicely - well as nicely as can be expected at 31 degrees. Did a series of 210 second clips with no gaps - I've found that this allows me to use short clips if the seeing is iffy or join them together again in PIPP for longer runs if the seeing holds. In the end I joined just 2 clips giving a 7 minute run.

BTW I experimented with NTSC format which gives 60 fps rather than PAL which only gives 50, but found that PAL is consistently better - absolutely no idea why.

Tried adding more clips and derotating but the result was no better and gave rings.

Pleased with the result - I reckon this is as good as I can get with the Canon, and hope to update soon to a dedicated camera. In fact I have a cunning plan...

For now: SW200P with Televue PMx5 (gives ~ x7) 7 minutes MOV file at 50 fps in video crop mode, (1/60 exp) ISO 400, best 2% only. PIPP, AS!2, Registax, light twiddle in PS. Hope you like it, happy to receive criticism.

 

 

[Tommohawk]

Excellent - no criticisms at all then!

[U Cyg]

Very nice from a DSLR.  Good luck getting your planetary cam!

[Tommohawk]

7 minutes ago, U Cyg said:

Very nice from a DSLR.  Good luck getting your planetary cam!

Thanks... stage one of the cam plan is complete; convincing myself.

Stage two is convincing the accountant...

 

[Pete Presland]

Some really nice detail there especially for a DSLR, hopefully you will get your cam.

[Stu]

Looks very nice to me, not so easy with a DSLR, but you've done a great job

[Tommohawk]

Thanks both. I've really enjoyed imaging with the 550D and had some pleasing results too even with planetary.

However... drum roll ... I now have an ASI290MC which I'm hoping will see first light tonight weather permitting. Another monster learning curve!

More later... maybe!

[knobby]

Great job, especially for a dSLR

[CraigT82]

Very nice work! I think you'll find using a dedicated planetary can much easier than the DSLR

[Tommohawk]

Thanks for the compliments.

On ‎01‎/‎05‎/‎2017 at 22:03, CraigT82 said:

Very nice work! I think you'll find using a dedicated planetary can much easier than the DSLR

I had a tinker with the ASI 290 Monday night. Fire capture works great - easy and intuitive, and managed 3 min runs at 150fps. Seeing was horrible, ad I think the sensor spacing was not optimal. Once I've had a proper go ill do a write up.

one huge advantage with DSLR is the big sensor... easy to find and then switch to crop mode. But I did ok with the ASI not least because it's easy to remove and switch to power mate.

of course new kit means clouds... So will have to wait!

[michael.h.f.wilkinson]

Very good DSLR planetary shot

[CraigT82]

On 03/05/2017 at 10:25, Tommohawk said:

Thanks for the compliments.

I had a tinker with the ASI 290 Monday night. Fire capture works great - easy and intuitive, and managed 3 min runs at 150fps. Seeing was horrible, ad I think the sensor spacing was not optimal. Once I've had a proper go ill do a write up.

one huge advantage with DSLR is the big sensor... easy to find and then switch to crop mode. But I did ok with the ASI not least because it's easy to remove and switch to power mate.

of course new kit means clouds... So will have to wait!

Yes fire capture is a great piece of kit, especially seeing as its free! 

What do you mean by sensor spacing? That shouldn't be an issue really (I think), unless you're getting internal reflections off something?

Looking forward to seeing some shots with the 290 

[Tommohawk]

31 minutes ago, CraigT82 said:

Yes fire capture is a great piece of kit, especially seeing as its free! 

What do you mean by sensor spacing? That shouldn't be an issue really (I think), unless you're getting internal reflections off something?

Looking forward to seeing some shots with the 290 

Spacing with the DSLR was about 63mm from the last element of the powermate, and if I screw the ASI to the Pm using the T ring adapter (ie not the 1.25" nosepiece) , spacing is only about 20mm. The last element of the powermate has quite a large diameter, about 24m, and having this only 20mm from a very small chip doesnt seem right. I'd love to plug the data into OSLO, but I dont have the powermate design data. If anyone does I'd be grateful!

I've never really understood the Powermate manufacturer's chart. It quotes the magnification according to the spacing from 0- 100mm measured from the "top surface". I cant think by top surface they mean the last refractive surface, because this would suggest it could be used with the last surface in contact with the sensor. Maybe they mean from the surface of the fully assembled item ie including the EP holder. In any event, because I know the optics worked beautifully with the DSLR I'm trying to replicate the spacing for now to minimise the variables and connecting with the EP adapter rather than the T ring adapter does this nicely.

Its possible my initial tests werent so good because I had high speed enabled on FC - not sure if you use that.. or what it actually does?

Once we get some clear skies I'll test it properly and do a report. Could be a while!!

 

[CraigT82]

Ah I see now. So with your DSLR did the image degrade if you had the sensor closer or further then 63mm from the powermate? 

I think they do mean from the top surface of the top lens, rather than the EP holder, as the EP holder screws off which would mess up that measurement?! 

I never use high speed on FC, I just get lots of dropped frames. I'm not sure but I think it changes 12bit ADC to 10 bit to achieve the higher speeds. I think that because with high speed off I get the quoted max frame rates for 12bit ADC, and with high speed ticked I get the max frame rates quoted for 10bit. Just a guess really. 

[Tommohawk]

1 minute ago, CraigT82 said:

Ah I see now. So with your DSLR did the image degrade if you had the sensor closer or further then 63mm from the powermate? 

I think they do mean from the top surface of the top lens, rather than the EP holder, as the EP holder screws off which would mess up that measurement?! 

I never use high speed on FC, I just get lots of dropped frames. I'm not sure but I think it changes 12bit ADC to 10 bit to achieve the higher speeds. I think that because with high speed off I get the quoted max frame rates for 12bit ADC, and with high speed ticked I get the max frame rates quoted for 10bit. Just a guess really. 

I never thought to test the DSLR with any other spacing as it seemed to work fine - but it wouldn't be possible to test it that close cos you can only connect via the T ring as I do, or via the 1.25" which would give even greater spacing.

Re FC Hi speed this thread suggests high speed is OK. Also if it switches from 12 bit to 10 bit ADC, what s the 16 bit tick box all about? And I though most folk used 10 bit, and claimed tht the effective bit rate increases when stacked. Its a mystery. I need to sight up to the ZWO user group and try and get some direct advice from Sam. The problem is that there isnt enough sky time to muck about with experiments - when its clear I want to crack on!

 

[Tommohawk]

On 06/05/2017 at 11:59, CraigT82 said:

Ah I see now. So with your DSLR did the image degrade if you had the sensor closer or further then 63mm from the powermate? 

I think they do mean from the top surface of the top lens, rather than the EP holder, as the EP holder screws off which would mess up that measurement?! 

I never use high speed on FC, I just get lots of dropped frames. I'm not sure but I think it changes 12bit ADC to 10 bit to achieve the higher speeds. I think that because with high speed off I get the quoted max frame rates for 12bit ADC, and with high speed ticked I get the max frame rates quoted for 10bit. Just a guess really. 

Will do a proper report on the ASI290 in a while - too much going on now!

Meantime re the powemate spacing, with the ASI 290 the log file reports that me FL is 5350 with PMx5  and SW200. This would suggest a magnification of 5.35. Looking at the PM chart, that implies a spacing of 15mm. That spacing tallies with the measurement from the top of the EP holder to the sensor. (The spacing from the last lens to the sensor is nearer 63.mm, so that clearly cant be the correct figure)

This suggests that the nominal 5x is at the top face of the EP holder. Seems to me that removing the EP holder unit, and connecting using the via the DSLR adapter direct to the ASI, whilst mechanically better, might compromise the optics. Maybe not!

[CraigT82]

All very interesting stuff.  But I wouldn't rely on those calcs and assumptions too much, not without physically measuring the focal length of your scope accurately (I measured the FL of my skyliner 200p which was supposed to be 1200mm but was closer to 1120mm in reality).

It'd be difficult to imagine that televue would manufacture the PM with a T2 connection which compromised the optical quality when used!

[Tommohawk]

1 hour ago, CraigT82 said:

 

It'd be difficult to imagine that televue would manufacture the PM with a T2 connection which compromised the optical quality when used!

What I'm saying is that the data they publish explains that different mags can be achieved by varying the sensor spacing, but that the nominal 5x reference point isn't obvious.

The design was intended to normalise the interface with eyepieces, so it seem likely that it's optimised for use with the EP holder in place. The EP holder can be removed, and an adapter used to connect to a DSLR, but the DSLR of course has a greater flange/sensor distance than a dedicated CMOS/CCD so this simply avoids having too much spacing.

It would be interesting to hear the designer's perspective, but because some ASI designs now have very short flange/sensor distances - to allow the inclusion of OAG/filters in the train - its possible that connecting directly (using an adapter designed (as I understand it) for a DSLR) could compromise the image.

That said, I've just checked the manufacturer's manual and it says "Any couplings for CCD cameras with female T-threads can be threaded onto the T-Ring Adapter." 

So maybe its OK?

What do most folk do with their Powermates - use the EP holder, or the T ring adapter?