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Equipment Discussions >> Mounts

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dr.who
scholastic sledgehammer
*****

Reged: 01/05/12

Re: Celestron VX mount new [Re: EFT]
      #5824088 - 04/26/13 10:51 AM

Per a post on another site Dan at pierplates.com has 8" top plates for the AVX now though they are not yet listed on his web site. He could probably gin something up for you to adapt it to that Skywatcher pier.

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PaulN
member


Reged: 10/12/08

Loc: Massachusetts
Re: Celestron VX mount new [Re: EFT]
      #5824205 - 04/26/13 11:42 AM

You know..this is a great forum for asking these types of questions and sharing of ideas.... thank you!

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Cow Jazz
professor emeritus


Reged: 11/24/03

Loc: Toronto, Ontario
Re: Celestron VX mount new [Re: EFT]
      #5828311 - 04/28/13 01:05 PM

Hey, gang, after following these posts since the "beginning", I picked up my new AVX on Friday from Brady at K-W Telescopes. We fired the mount up in the store, he gave my wife a Celestron toque, and we were on our way. Assembled it last night for the first time and took it out to the back deck for a quick runthrough with my 80ED riding on it. I leveled the tripod, roughly aimed the mount north, powered up and did a "rough" 2-star alignment, and every go-to was there in the 25mm EP. I am happy, happy, happy! Now to learn all the details and really have fun with this thing. I'll be starting with unguided piggyback AP with my DSLR and 200mm lens, then hope to get an autoguider and get serious with it.

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SunBlack
scholastic sledgehammer


Reged: 05/05/11

Loc: Rome (IT)
Re: Celestron VX mount new [Re: Cow Jazz]
      #5832073 - 04/30/13 11:44 AM

To all owners: the attachment of tripod to mount is EQ5/HEQ5/Vixen GP-GPD style?

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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron VX mount new [Re: SunBlack]
      #5832252 - 04/30/13 12:51 PM

It's AVX style.

I've run a tape measure over mine:

The pier plate needs to be 130mm in diameter with a 60mm clearance hole in the centre and an azimuth adjuster consisting of a 10mm square post spaced 53mm from the centre.

The plate needs to be at least 18mm thick. It should not be too big because the altitude adjusting bolt projects below the plate at a radius of 90mm.

As has been said before this is similar to the CG5 except for the position of the Azimuth adjuster. I don't know about the other mounts but it could be different to all of them.

The hold bolt is central and I think it's M10.

Any small metal working shop could make a plate to fit, although I'd take the mount along rather than relying on measurements from some guy on the internet.

Chris


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nine44
sage
*****

Reged: 01/19/13

Re: Celestron VX mount [Re: EFT]
      #5833423 - 04/30/13 11:03 PM

Regarding re-alignment of the AVX after a successful polar align... It seems there may be an easier way, but I'm not seeing it.

I generally do a 2+4 alignment and then polar align. If there is significant correction during the polar align process, it can effect pointing accuracy, so it is best to recalibrate the mount. After polar alignment, it would be easier to just send the mount back to the home position and do a new alignemnt.

Right now, I have to unsync my polar align star. Then back out of the alignment menu. Slew to one of the original alignment stars. Then go back to the align menu and select alignemnt stars and then "replace." Then back out and slew to the second star--then back to alignment stars and "replace." Hopefully you get the picture.

Anyone know of a way to send the mount back to its home position after a polar alignment? Or am I missing something BIG?


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FacEngRet
member


Reged: 02/27/13

Re: Celestron VX mount [Re: nine44]
      #5833454 - 04/30/13 11:31 PM

You can go back to the home position by pressing MENU/Utilities/Home Position/GOTO and then pressing enter. I made a small laminated copy of the menu tree found on page 23 and 24 of the manual and keep it in my shirt pocket. I used it a lot at first, but now, a couple months later, a rarely look at it. I usually do what you want to do. I un-sync from the polar align star, goto home and do a new 2+4. Doesn't take long and I have had good success doing so.

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dr.who
scholastic sledgehammer
*****

Reged: 01/05/12

Re: Celestron VX mount [Re: FacEngRet]
      #5833588 - 05/01/13 02:14 AM

Actually you would push "Back" until you see the "Celestron AVX" displayed then follow FacEngRet's directions.

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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron VX mount [Re: dr.who]
      #5833630 - 05/01/13 03:44 AM

The simplest procedure to get a good alignment after an ASPA is to do nothing. At most do an unsync or a new sync.

The scope knows the polar alignment error and when ASPA is done rotates the alignment matrix by the polar alignment error.

It is easy to test this, do a few slews to bright stars, centre them and use the Identify procedure. This will give you the distance the mount thinks you are from the star.

Chris


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nine44
sage
*****

Reged: 01/19/13

Re: Celestron VX mount [Re: cn register 5]
      #5833818 - 05/01/13 08:22 AM

Quote:

The simplest procedure to get a good alignment after an ASPA is to do nothing. At most do an unsync or a new sync.

The scope knows the polar alignment error and when ASPA is done rotates the alignment matrix by the polar alignment error.

It is easy to test this, do a few slews to bright stars, centre them and use the Identify procedure. This will give you the distance the mount thinks you are from the star.

Chris




Chris--my experience is--after doing a 2+4 alignment and making a significant polar alignment adjustment, the slews are off. My AVX doesn't seem to be adding the erro rlike you mention. Also, the user manual suggests re-aligning after a polar adjustment. INterested to know if I am missing something.


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron VX mount [Re: nine44]
      #5833870 - 05/01/13 09:04 AM

Nobody needs to take my word for this.

You can all measure the change in alignment accuracy that an ASPA causes:
  • Do an alignment as normal.
  • Slew to a few stars and use the Identify function to get an idea of the pre ASPA alignment accuracy.
  • Do the ASPA.
  • Slew to a few stars and use the Identify function to get an idea of the post ASPA alignment accuracy.

This process is called Science. People have been doing this sort of thing to find things out for about 500 years now.

Chris


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nine44
sage
*****

Reged: 01/19/13

Re: Celestron VX mount [Re: cn register 5]
      #5833890 - 05/01/13 09:12 AM

Chris--wasn't trying to insult you. I'm just trying to understand how it works. There are alot of scientists on this forum--and all of us are pursuing knowledge--sometimes asking stupid questions to get to a deeper understanding. All I know (which is not much) is that after the polar alignment, my GOTOs are off and the manual seems to echo what I'm experiencing. I guess I'm wondering if my mount is accounting for the calculated error you mention yours is.

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bunyon
Post Laureate
*****

Reged: 10/23/10

Loc: Winston-Salem, NC
Re: Celestron VX mount [Re: nine44]
      #5833928 - 05/01/13 09:31 AM

It may well have to do with how large an initial polar alignment error you have. I've been polar aligning EQs for over 30 years and, frankly, my initial alignments are pretty good.

Not sure what the average is, but when I do ASPA with the VX, it is rare to not have the target star in the eyepiece. So adjustments are minimal. Given that experience, I find that once I unsync the target star, my gotos are fine.

It may be that if your initial alignment is too far off, the computer can't correct. An easy experiment, and I'll try it next time I'm just playing around, would be to intentionally set up with the mount far from aligned.

In any case, I strongly recommend you try to get as close to aligned as possible at initial setup. If you are doing this and you're pretty close and the gotos are off after ASPS, I'd be interested to here.


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dcbrown73
member


Reged: 06/23/12

Loc: Lower Connecticut
Re: Celestron VX mount [Re: powerstroke01]
      #5833945 - 05/01/13 09:42 AM Attachment (29 downloads)

My Celestron VX mount just arrived yesterday. It's my first EQ mount so I've got some learning to do. I purchased it for a new ES 80mm APO refractor I bought at NEAF, but fully plan on throwing my 8SE OTA on it also from time to time.

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Stew57
Carpal Tunnel
*****

Reged: 05/03/09

Loc: Silsbee Texas
Re: Celestron VX mount [Re: cn register 5]
      #5834177 - 05/01/13 11:43 AM

I have done
2+4 alignment
Slew to objects and see where on my camera chip they fall
Do ASPA
Slew to same objects and see where on the camera chip they fall.

Depending on how far off my original polar alignment was I may have to redo an alignment to get my original accuracy back. Derik at teamcelestron will substantiate that.

I have not asked but I notice that the calibration stars are removed after ASPA and maybe that is where the accuracy discrepancy occurs.

Anyway my science data does not seem to be the same as your science data but does seem to correlate well with Nine44's. Those kind of discrepancies in data have been going on for as long as scientific enquiry has been practiced. The key to science is finding out why they are there.


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Carl N
sage
*****

Reged: 03/18/12

Loc: San Diego, CA
Re: Celestron VX mount [Re: Stew57]
      #5834251 - 05/01/13 12:20 PM

I may not use the easiest method, but I do the 2+4, then ASPA. Then I go to home position, turn off my mount, turn it back on, and do the 2+4 again. By rebooting, I don't have to unsync and replace alignment stars.

I have found, using a 5mm illuminated cross hair eyepiece, that if I do the 2+4, ASPA, reboot, 2+4 again, ASPA again, reboot, 2+4 again - that I get really tight results.

By doing that sequence twice I eliminate micro error and when I use identify, I am spot on.

Carl


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Jeff2011
Carpal Tunnel
*****

Reged: 01/01/13

Loc: Sugar Land, TX
Re: Celestron VX mount [Re: SunBlack]
      #5834261 - 05/01/13 12:24 PM Attachment (85 downloads)

Quote:

It'd be nice if any owner could try some unguided pics with dslr and 200-300mm FL lens for testing tracking accurancy...




Not exactly what you asked for, but here are my results with a 430mm focal length refractor. These results also show the accuracy of an ASPA with DSLR star drift results after the ASPA. This is unguided, no PEC.

Edited by Jeff2011 (05/01/13 12:31 PM)


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bunyon
Post Laureate
*****

Reged: 10/23/10

Loc: Winston-Salem, NC
Re: Celestron VX mount [Re: Jeff2011]
      #5834361 - 05/01/13 01:07 PM Attachment (79 downloads)

I put this up in another thread but, perhaps, not many saw it.

I roughly aligned by sight, did 2+4, did ASPA. Gotos were within the field of view after unsyncing from target star in ASPA. I then did guided and unguided imaging. I then did a PEC recording and again did guided and unguided. I also tested how far I could go with a guided image.

EDIT: the RA drift is scanning east for 30s and then west for 25s. I found no adjustments necessary after ASPA.

The results are in the image. I used a C8 with reducer (1200mm EFL) and Orion finder guider. I think certainly with PEC unguided for a couple minutes at 200mm should be fine. Guided you could go as long as you want.

I did ask in the other thread, why the fascination with unguided? It's not hard to guide.

EDIT2: Since we're talking science, the sample size here is much bigger than it looks. 150s unguided pre-PEC had 25% failure rate in 20 tries. I got 20 good ones after PEC. Unfortunately, n=1 for the 900s image. But in 20 300s subs, all were fine with PEC and guiding.

Edited by bunyon (05/01/13 01:10 PM)


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Jeff2011
Carpal Tunnel
*****

Reged: 01/01/13

Loc: Sugar Land, TX
Re: Celestron VX mount [Re: bunyon]
      #5834503 - 05/01/13 02:11 PM

Quote:


I did ask in the other thread, why the fascination with unguided? It's not hard to guide.





My results are from another thread as well. I also received a similar question from another CN member in that thread. I think it has to do with us AP newbies trying to take it one step at a time to become proficient with short duration unguided shots before adding the addtional equipment and learning curve required for autoguiding. So our interest is in how long we can track before needing to go with autoguiding. The problem that I see with unguided AP is that it is not consistent. For example at 1.5 minutes only 44% were keepers. So I do see the wisdom in guiding. I plan on ordering a QHY5L-II guide camera and a guide scope soon, so I am headed in that direction.


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nine44
sage
*****

Reged: 01/19/13

Re: Celestron VX mount [Re: Jeff2011]
      #5834524 - 05/01/13 02:23 PM

Turn key guiding is a $300 proposition, but it has really help me and likely has maintained my interest / reduced my frustration as I learn. Rather than fight my mount all night long, I just have to get it close and then my SSAG takes over. My light polluted location does prevent me from taking exposures beyond about 1 minute. So winning the accurate tracking / guiding duration contest isn't a goal for me anyway. I really need to get to a dark site.

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