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Celestron CPC-1100 + PEMPro 2 = Results !!

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#1 Psyire

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Posted 01 April 2010 - 10:54 PM

So last night I spent all night outside in my 3rd attempt at running a proper Periodic Error asessment and correction with PEMPro 2. The Results are in!

Specs:
Mount: Celestron Nexstar CPC1100 w/ Stainless Steel Ball Bearing Modification (Custom Wedge Mounted)
Scope Used: Piggybacked Equinox 80ED w/ Barlow yielding 1.08 arc-sec/pixel.
Camera: Philips SPC900NC
Skies: Transparency 3/5, Seeing 4/5 (Quite good for here)

So my goal was simple.. Gather a bunch of data with PEC Off, Create the PE Curve and upload it to the mount, and then gather a bunch more data with PEC On. Compare results. What I wasn't prepared to do was pick my jaw up off the floor after it was all said and done!

PE Data from first run. (PEC Off)

Posted Image
The PE Curve was then created from this data set which yielded these numbers: PE +14.4/-11.9 arc-secs, RMS Error: 4.947

So I uploaded this PE Curve to the mount and started gathering more data.

PE Data from second run. (PEC On)

Posted Image
The PE Curve was then created from this data set which yielded these numbers: PE +2.7/-2.6 arc-secs, RMS Error: 2.388

And finally here is a screenshot of the comparison graph:
(Red= Before, Blue= After)

Posted Image

I am extremely happy with these results using this mount! :jump: I just hope the translate into much less work for my autoguider so my overall imaging experience gets much easier.

If anybody is interested in looking at my raw data you can download it here: CPC-PEMPro Data

One thing I did this time around that I'd like to point out was balance the fork arms carefully. (East/West) Prior to this I've never worried about it, but I'm sure it made a big difference in my overall numbers.

One thing I found when searching for CPC Periodic Error Data is that it was hard to come by. I hope this helps some people out in that regard. The next test will be Imaging, however the weather has gone bad again so it might be a bit.. I'll definately post a follow up in this thread. Thanks for reading! Any input is appreciated.

#2 Yedgy

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Posted 02 April 2010 - 02:33 AM

Nice job! I'll give you the benefit of the doubt that this isn't an April Fool's joke. You should repost your 2nd PEMPro run image, as the one in your post seems to be a copy of the first run.

Tony

#3 mclewis1

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Posted 02 April 2010 - 08:51 AM

These results shouldn't be a surprise. The well regarded CGE mounts and Nexstar GPS scopes shared virtually the same motors and gears, the bearings however were different due to the very different mount types (gem vs. Alt Az/wedge). CPCs have only changed a little bit from the Nexstar GPS scopes, they still have the same size worm/spur gears and motors.

Nice to see someone take the time to get some numbers on the CPCs.

#4 lambermo

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Posted 02 April 2010 - 10:29 AM

I don't get this. Your data shows :
Without PEC : PE +14.4/-11.9 arc seconds -> 26.3 arc seconds peak-to-peak
With PEC : PE +2.7/-2.6 arc seconds -> 5.3 arc seconds peak-to-peak
Yet your 'comparison graph' shows a peak-to-peak of 26.31 'before' and a 2.0 arc seconds 'after'. Where does this 2.0 come from :confused:

ps. as Yedgy already mentioned please repost your 2nd PEMPro run image.
-- Hans

#5 Psyire

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Posted 02 April 2010 - 10:41 AM

Oops, got in trouble with the copy/paste function. lol I edited the above post to reflect the proper screenshots.

#6 Psyire

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Posted 02 April 2010 - 11:06 AM

Hans/Tony, thanks for pointing that out. I went back to PEMPro and ran the curves and comparisons again and came up with the proper numbers. I'm not sure why it didn't do this the first time but it looks good now. Of course 5.31 arc-secs Peak-Peak isn't as good as the 2.0, but it's still a great improvement! :jump:

Note: My original post has been updated to reflect this change!

#7 Psyire

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Posted 02 April 2010 - 11:23 AM

These results shouldn't be a surprise. The well regarded CGE mounts and Nexstar GPS scopes shared virtually the same motors and gears, the bearings however were different due to the very different mount types (gem vs. Alt Az/wedge). CPCs have only changed a little bit from the Nexstar GPS scopes, they still have the same size worm/spur gears and motors.

Nice to see someone take the time to get some numbers on the CPCs.


Mark, I agree completely. I've always said that the CPC would give the CGE a run for it's money and now I've got the numbers to prove it. If you loaded a CGE with a C11 & an 80ED I'm pretty sure the numbers wouldn't be much different than mine...

#8 lambermo

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Posted 02 April 2010 - 02:51 PM

Thanks for clearing up the data.
I've added your results to my list of astrophotography capable mounts at http://lambermont.dy...g/astro/pe.html you're the 75th entry :thewave:
Now I need a payload measurement/guess for the 1100. Anyone ?

As well as 800 and 925 data ...

-- Hans

#9 Mike Clemens

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Posted 02 April 2010 - 03:42 PM

Great results! Thanks for posting them.

#10 Mike Clemens

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Posted 02 April 2010 - 03:47 PM

lambermo, you link to my PEC picture on your page, (AP1200GTO) that was with 80 pounds of payload and 55 pounds of counterweights.

#11 Psyire

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Posted 03 April 2010 - 03:31 PM

Thanks for clearing up the data.
I've added your results to my list of astrophotography capable mounts at http://lambermont.dy...g/astro/pe.html you're the 75th entry :thewave: -- Hans


Nice! Thanks for posting that link as I haven't seen your page before. Interesting to say the least.. Do you want the payload rating of just the scopes+equipment or the whole shebang with fork arms and everything?

#12 lambermo

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Posted 04 April 2010 - 03:06 AM

Do you want the payload rating of just the scopes+equipment or the whole shebang with fork arms and everything?


Just the payload (OTA+equipment) so it can be compared to the other mounts. This is a little hard as your OTA is integrated ;-) and Celestron does not clearly specify its mass nor the maximum attachment/piggy-back load AFAIK.
So I'm fine with an educated guess here ;-) I had to do the same for Meade's LX200.

ps. payload does not include counterweigths. This may sound trivial but vendors like Vixen mention 'load capacity' and 'load weight', which is payload plus counterweights :mad:
pps. Another payload thing is the reported payload of Takahashi's EM-11 : it's 9 kg at http://www.takahashi...cifications.php and 11 kg at http://takahashiamer...ttom_mounts.htm :confused:

#13 Patrick

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Posted 04 April 2010 - 01:56 PM

Psyire,

That looks really good. With PEC runningand at shorter focal lengths and exposures you could probably get away with not guiding at all.

Patrick

#14 Psyire

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Posted 04 April 2010 - 02:33 PM

Just the payload (OTA+equipment) so it can be compared to the other mounts. This is a little hard as your OTA is integrated ;-) and Celestron does not clearly specify its mass nor the maximum attachment/piggy-back load AFAIK.
So I'm fine with an educated guess here ;-) I had to do the same for Meade's LX200.


Not sure if others would agree but my educated guess is 25kg. The CPC mounts seem to be able to hold anything the CGE except there is no 14" SCT version.

#15 Psyire

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Posted 04 April 2010 - 02:41 PM

Psyire,

That looks really good. With PEC runningand at shorter focal lengths and exposures you could probably get away with not guiding at all.

Patrick


I was thinking that too Patrick, expecially DSLR lens work. Which it looks like i might have to try! (50mm 'ish)

#16 DaemonGPF

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Posted 04 April 2010 - 08:25 PM

This is good news. I'll be doing this with an NS8 GPS shortly. I'm interested to see what the difference would be with the lighter config, and on the older design.

#17 mclewis1

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Posted 05 April 2010 - 09:09 AM

The CPC mounts seem to be able to hold anything the CGE except there is no 14" SCT version.

I wouldn't go quite that far. The fork mounting puts a lot of stress on the azimuth bearing since there is no counterweight. There is no way I'd want to put 60+lbs of instrument payload on a CPC or NS GPS fork mount. This is especially true at lower lattitudes ... the lower the less the mount will be able to carry, the higher the more the mount acts like an Alt Az and the less stress on that Azimuth bearing there is.

I think 20kgs/44lbs is probably a safer number that would cover a wider range of setups on a fork mounted CPC or Nexstar GPS scope.

#18 Psyire

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Posted 05 April 2010 - 02:43 PM

I wouldn't go quite that far. The fork mounting puts a lot of stress on the azimuth bearing since there is no counterweight. There is no way I'd want to put 60+lbs of instrument payload on a CPC or NS GPS fork mount. This is especially true at lower lattitudes ... the lower the less the mount will be able to carry, the higher the more the mount acts like an Alt Az and the less stress on that Azimuth bearing there is.

I think 20kgs/44lbs is probably a safer number that would cover a wider range of setups on a fork mounted CPC or Nexstar GPS scope.


Valid points for sure. 20kgs seems like a reasonable number.

#19 Psyire

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Posted 22 April 2010 - 04:28 PM

UPDATE
--------

I was finally able to test out the effectiveness of having PEC enabled while imaging a few nights ago. Here are the results:

M106, 5min subs, C11 @ F/6.3 = FL:1763mm (PEC On & Autoguiding)
(Click for 1200 Wide)
Posted Image

M51, 10min subs, C11 @ F/6.3 = FL:1763mm (PEC On & Autoguiding)
(Click for 1200 Wide)
Posted Image

All in all I think it's working great, I couldn't get these results with relying on autoguiding alone.

#20 Peter in Reno

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Posted 22 April 2010 - 04:51 PM

Did you use OAG or guide scope? If you used guide scope, did you see image shift in between subs especially for 10 minute subs?

BTW, very nice photos!

Peter

#21 Psyire

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Posted 22 April 2010 - 05:19 PM

I used an 80mm guide scope, and there was a bit of shift between subs. I hope to have an OAG setup soon for when imaging through the C11.

#22 Patrick

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Posted 22 April 2010 - 09:47 PM

Psyire,

I'm stunned! Absolutely fantastic images! I'm in the process of installing a wedge on my pier and getting setup for imaging with my CPC1100. It's nice to know what the scope and mount are capable of.

Great job!

Patrick

#23 Psyire

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Posted 24 April 2010 - 02:51 PM

You're too kind Patrick, thanks for your compliments!

#24 astrovienna

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Posted 30 April 2010 - 01:26 PM

Hey Craig, I just wanted to let you know my results on a similar setup. I've been learning Pempro the last few nights, and finally got familiar enough with it to get some results. My CPC1100 started at about 33 arcsecs peak to peak. Post-Pempro it's 4.7 arcsecs, with an RMS of 0.96. Nice!

I was surprised because I didn't think my data was all that great. I got better data in a second run last night, and I'll experiment with that tonight to see if it works even better. I'll post in a new thread when I get some final results.

Kevin






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