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AlexN
Pooh-Bah


Reged: 08/09/08
Posts: 1202
Loc: Brisbane - Australia
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2760650 - 11/20/08 12:19 AM

I use the same setup, And at F/6.3 I dont have a problem running 20 ~ 25 min exposures... I sometimes spend up to 40 minutes tweaking the balance until it is perfect... with this much weight on the mount, your balance has to be SPOT ON!! DEC balance should be 100% perfect, I use a weight to unbalance it by 2 ounces in RA (heavy on the east) I do this using a small bag attached to the bottom of the counter weight shaft, with a 4x 0.5oz fishing sinkers in it. I balance it to be EXACTLY balanced in RA with the bag attached, then remove the bag before imaging.

Mirror shift could be a problem, but I've found its not for me, unless goes really close to the meridian..

Do you have your ST80 on top of your C11 or side by side? I use mine side by side, Doing this is good for a few reasons. 1. You keep the weight closer to the polar axis, thus putting less strain on the mount.
2. You have less chance of flexture (although, with the Losmandy bar and saddle, your flex there should be minimal.

If I think of anything else, I'll post back

You have a nice, and very capable setup! and once you iron out this little issue, you'll love it to bits (as I do)

Oh, Collimate the scope... I know people say its not overly important on the SCT scopes... It is... Check it, because the stars looking slightly out of shape could be collimation....

Cheers.
Alex.

--------------------
Custom Made 10" F/3.8 Newtonian Astrograph
EQ6-Pro
SBIG ST-8300M
FLI CFW 2-7
Astrodon 5nm NB Filters
Astrodon I series LRGB
OAG + QHY5


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AlexN
Pooh-Bah


Reged: 08/09/08
Posts: 1202
Loc: Brisbane - Australia
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: AlexN]
      #2760698 - 11/20/08 01:22 AM

Oh thats it... Drift align the mount using the ST80 on its own, with a reticule ep and a 2x barlow, or using a camera with computer aided drift align routine (K3CCD tools has a good one, or a program like EQ Align or WCS) drift align it until you see no drift at all for 10mins at the ep, or untill your software program reports little to no drift, Park the mount, then set it up with the C11+ST80 etc... Thats what I do here, I drift align with just my 90mm refractor and my DBK31 to measure drift through K3CCD tools. Then swap out the 90mm for the side by side C11 + ST80, balance it up, do my star alignment, and away I go...

I strongly recommend using more than just the polar scope for imaging with long focal lengths (2.8m of the C11 is LOOOONG!)

--------------------
Custom Made 10" F/3.8 Newtonian Astrograph
EQ6-Pro
SBIG ST-8300M
FLI CFW 2-7
Astrodon 5nm NB Filters
Astrodon I series LRGB
OAG + QHY5


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: AlexN]
      #2760720 - 11/20/08 02:01 AM

That's a great idea about drift alignment using a smaller and lighter scope. I hope it's not too time consuming.

My guide scope is currently mounted on top of C-11 via ADM's mini-dovetail system.

Thanks,
Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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AlexN
Pooh-Bah


Reged: 08/09/08
Posts: 1202
Loc: Brisbane - Australia
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2760731 - 11/20/08 02:36 AM

Once you get the hang of drift alignment, it only takes 25 ~ 30 mins to get it pretty good. if you use a your SSAG and K3CCD tools (or one of the other programs) it can take as little as 15 minutes between setup and perfect alignment.

--------------------
Custom Made 10" F/3.8 Newtonian Astrograph
EQ6-Pro
SBIG ST-8300M
FLI CFW 2-7
Astrodon 5nm NB Filters
Astrodon I series LRGB
OAG + QHY5


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Strgazr27



Reged: 10/04/04
Posts: 7104
Loc: StonyHill Observatory
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: AlexN]
      #2760756 - 11/20/08 03:54 AM

Keep in mind that doing a drift alignment with the 90 will get you close but when imaging through the 11, especially at it's native Fl will show errors in your PA that the 90 would not show. This will be less evident on shorter length groups of images but start stacking 3-4 hours of subs and it will show.

CS's

--------------------
Bobby

http://www.strgazr27.zenfolio.com


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AlexN
Pooh-Bah


Reged: 08/09/08
Posts: 1202
Loc: Brisbane - Australia
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Strgazr27]
      #2760760 - 11/20/08 04:12 AM

90 + 2.5x powermate + DBK for alignment, When K3CCD tools reads less than 1 arcsec per minute of drift at 1224mm focal lenght, I figure with guiding the C11 should do fine.. (I almost exclusively run my C11 @ F/6.3 - 1756mm focal length)

--------------------
Custom Made 10" F/3.8 Newtonian Astrograph
EQ6-Pro
SBIG ST-8300M
FLI CFW 2-7
Astrodon 5nm NB Filters
Astrodon I series LRGB
OAG + QHY5


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: AlexN]
      #2761078 - 11/20/08 10:33 AM

PHD is keeping the guide star dead center with 80mm guide scope, why do successive frames (e.g. 10 minutes each frame) using C-11 continiously shift in the SAME direction. I don't know if the direction is RA or Declination. Each frame looks okay but if I stack all frames without alignment, I see huge star trails. Do you really think perfect polar alignment will solve this? I always thought it was flexure but I cannot find it since everything is very tight. I use clam shell type tube rings instead of three screws to secure guide scope. See my signature for equipment. I am leaning toward mirror shift or re-balance mount using "East heavy" method.

Celestron has been making SCT for so long, why haven't they improve the focusing system to prevent mirror shift? I have JMI Motofocus and I was hoping once the focus is set, the Motofocus keeps the focuser from moving or shifting because the motor is pretty stiff when not engaged.

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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David PavlichAdministrator
Transmographied


Reged: 05/18/05
Posts: 21117
Loc: Mandeville, LA USA
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2761112 - 11/20/08 10:50 AM

Your problem isn't mirror shift. Gravity takes care of that unless you're imaging up to the meridian and have to do a flip.

It's either a flexing problem or what I think is the culprit, polar alignment. Strip everything off of the mount except the C11. As already mentioned, the higher the mag, the better the alignment. Drift takes some time, but if you're going to do 10+ minute subs, it has to be very close. Add to that, the native f10 and you're really pushing the system.

Now you know why serious imagers by those big, expensive mounts.

And the east heavy balance thing. If you're imaging east of the meridian, the mount needs to be SLIGHTLY counterweight heavy. That ensures that the worm is always engaged. When the mount guides in RA, it either speeds up or slows down the mount, it doesn't reverse directions. Hence, the need to keep the worm engaged 100% of the time. A perfectly balanced mount could allow the worm to becomes "unengaged" when the guider tells it to slow down.

David

--------------------
Money can't buy happiness, but it sure makes misery easier to live with.



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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: David Pavlich]
      #2761191 - 11/20/08 11:40 AM

David,

Even with the C-11 alone, it's still heavy and very difficult to turn the latitude bolts and not worth the risk damaging the bolts or threads in mount. Thanks for the suggestion. Probably drift alignment with smaller scope is more accurate than using Polar scope. When I use polar scope, I use polar finder software and once I align Polaris where it should be in polar scope, I rotate RA to make sure Polaris remains in circle. I thought this method is pretty accurate. I guess I thought wrong.

And the east heavy balance thing, you said mount needs to be CW heavy when imaging east of meridian. What about imaging west of meridian? Should it be Scope heavy?

Thanks,
Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2761396 - 11/20/08 01:37 PM

Hello,

After reading this thread and research from other web sites, I think my issue is imperfect polar alignment along with long focal length of my C-11. I found a very informative web site describing drift alignment. It can be found at:

http://www.petesastrophotography.com/

Click on "Drift Technique" under "Polar Alignment" at the left. The web site also has tutorial simulator of how to perform drift alignment with your computer.

Clear Skies and Tiny Stars,

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2761508 - 11/20/08 02:53 PM

What about my Atlas EQ-G tripod? Could it be too wimpy to carry 38 pounds of scopes plus 44 pounds counter weights plus 32 pounds mount head which totals 114 pounds of loads on my tripod? Could this be the source of flexure?

I so hate dealing with many unknowns and continue to spend money until the issue is fixed.

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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X-Lurker
Underpaid Slacker


Reged: 09/12/06
Posts: 763
Loc: N.W. Ark.
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2761740 - 11/20/08 04:43 PM

Has PE correction been mentioned?

--------------------
Clear Skies,
Larry

I wasn't sick...I just called in uninterested



Glob

AOAS Member
10" Reflector (Cloud Magnet)
AT66ED
Pier Mounted EQ-6 (Powered by EQMOD)
Orion SVP 127
DSIc
SPC 900NC
Cloud Filter (On Order)



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donsinger1
sage


Reged: 10/28/07
Posts: 307
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2761749 - 11/20/08 04:48 PM

I think you are darn close to the limits.......

Don

--------------------
Fun Stuff:)
Portland, OR


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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: donsinger1]
      #2761805 - 11/20/08 05:13 PM

I saw this in Cats & Casses thread about a pretty cool Off Axis Guider:

http://www.taurus-tech.com/tracker.htm

I read several reviews via Google and it received pretty high marks. I have read many people hates OAG but this is a really cool gadget.

OAG could eliminate the need to use guide scope mounted on main scope and save weight and possible greatly reducing flexure.

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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David PavlichAdministrator
Transmographied


Reged: 05/18/05
Posts: 21117
Loc: Mandeville, LA USA
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2761913 - 11/20/08 06:10 PM

Quote:

David,

Even with the C-11 alone, it's still heavy and very difficult to turn the latitude bolts and not worth the risk damaging the bolts or threads in mount. Thanks for the suggestion. Probably drift alignment with smaller scope is more accurate than using Polar scope. When I use polar scope, I use polar finder software and once I align Polaris where it should be in polar scope, I rotate RA to make sure Polaris remains in circle. I thought this method is pretty accurate. I guess I thought wrong.

And the east heavy balance thing, you said mount needs to be CW heavy when imaging east of meridian. What about imaging west of meridian? Should it be Scope heavy?

Thanks,
Peter




I understand your problem with the Alt bolts. I owned an Atlas and it was always a concern.

And you're correct, you want to be scope heavy if your object is west of the meridian for the same reason...keeping the worm engaged.

I don't think your tripod is too weak, however how is it set up? Is it on concrete or on the lawn? If it's on concrete or asphalt, you need vibration dampeners under the legs. Actually, the lawn is the best place because it's so stable. You just have to have conditions very close to perfect because of the loading on the Atlas.

David

--------------------
Money can't buy happiness, but it sure makes misery easier to live with.



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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: David Pavlich]
      #2761940 - 11/20/08 06:24 PM

Quote:

I understand your problem with the Alt bolts. I owned an Atlas and it was always a concern.

And you're correct, you want to be scope heavy if your object is west of the meridian for the same reason...keeping the worm engaged.

I don't think your tripod is too weak, however how is it set up? Is it on concrete or on the lawn? If it's on concrete or asphalt, you need vibration dampeners under the legs. Actually, the lawn is the best place because it's so stable. You just have to have conditions very close to perfect because of the loading on the Atlas.

David




The tripod is on concrete pad via Orion's vibration dampeners. I marked the tripod points on concrete with latex paint so that the tripod is always at the exact same spot every time to make polar alignment much easier.

Peter

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2762120 - 11/20/08 08:03 PM Attachment (66 downloads)

This was my original target before I started having problems. Later that night I imaged M1 as shown earlier in this thread.

NGC891
C-11 at F/10, 2800mm F/L
2 frames of 15 minutes each
1 frame of 10 minutes

Imagine what this would look like if I had image it all night with 15 minutes (or longer) each frame!!!! If I only knew exactly the issue I am having.

Peter

Attachment

--------------------
Astro-Physics Mach1GTO GEM
Celestron 8" EdgeHD OTA
Atik 460EX mono CCD camera
SX 7 position 36mm filter wheel
Astrodon 36mm LRGB, Ha 5nm, OIII 5nm, SII 5nm
Lodestar autoguider
Hutech OAG with Helical focuser
SXVR-M25C CCD color camera
Nagler 31mm, Ethos 13mm & 8mm
Peter's Galleries



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RobertED
Carpal Tunnel


Reged: 07/11/03
Posts: 2766
Loc: Johnston, RI
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2762279 - 11/20/08 09:37 PM

These really are beautiful images...nice work Peter!!

--------------------
41 deg 51'08.20" N , 71 deg 32'08.32" W


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David PavlichAdministrator
Transmographied


Reged: 05/18/05
Posts: 21117
Loc: Mandeville, LA USA
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: Peter in Reno]
      #2762475 - 11/20/08 11:29 PM

Quote:

This was my original target before I started having problems. Later that night I imaged M1 as shown earlier in this thread.

NGC891
C-11 at F/10, 2800mm F/L
2 frames of 15 minutes each
1 frame of 10 minutes

Imagine what this would look like if I had image it all night with 15 minutes (or longer) each frame!!!! If I only knew exactly the issue I am having.

Peter




I don't know...after looking at your NGC891, I think you may be asking too much of your imaging setup. You're shooting at f10 on a mount that is over its advertised limit. 891 looks quite nice to me.

My one "successful" image that I took with a C11 was of M51 with a modified 350D. I used an Astro-Physyics focal reducer (I don't remember the part #) and noticed no vignetting. Perhaps it's different with a CCD camera, but I had no problem reaching focus with it. Is it possible that your focal reducer is somehow not up to snuff? I'm grasping at straws here.

I think if you get your PA a little closer, your problems are going to disappear, especially if you can image with a FR. Or you can build an observatory and get the Atlas on a pier. And that means polar align and you're done!

David

--------------------
Money can't buy happiness, but it sure makes misery easier to live with.



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Peter in Reno
Post Laureate


Reged: 07/15/08
Posts: 4566
Loc: Reno, NV
Re: Atlas EQ-G, imaging C-11, 80mm ST, PHD Guiding new [Re: David Pavlich]
      #2762542 - 11/21/08 12:36 AM

An observatory would be nice if I have the time and space to build one.

I have a Celestron focal reducer. Right now the only place I can mount it is right at the rear cell of C-11. But I have to have about 3" - 4" extension to the camera because the diameter of Orion StarShoot camera is so big that it hits the JMI Motofocus without the extension. I think the extension is causing excessive vignetting. I have not yet figured out how to place the FR at the camera or in between the camera and extension. I am sure I can but I have not been looking hard enough.

Actually the advertised load capacity of the mount is 40 pounds and my main and guide scopes plus mini-dovetail and tube rings weighs 38 pounds. So that's two pounds below the advertised weight (not including counter weights).

Peter

Edited by Peter in Reno (11/21/08 12:47 AM)


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