CGEM hypertune

[Tony_]

I'm currently considering getting a hypertune kit for my CGEM which are around $220. I don't consider that expensive but is it worth it for what you get or are there better options? Are the ptfe and ceramic worm bearing set etc. standard parts that can be bought in Australia? If there's not much to save and the kit has everything I need (except some tools) then I prefer not to have the hassle of sourcing parts.
The kit would be the easy way - but does it improve the mount much? I want to improve the PE for unguided imaging and improve guiding.

Has anyone here bought the hypertune kit or other parts for a CGEM? I know the CGEM isn't a great imaging mount - but I want to get the best out of hat I currently have.

Regards,
Tony.

[toc]

Mine is on the way - I've noticed a few issues with stiff movement in RA, as we'll has poor guiding on targets to the north, which I think are related.

[Tony_]

Thanks Tim,

It will be interesting to see exactly what you get. If possible could you post a picture of the kit?Did you get the ceramic worm gear option also?
I am also interested to see if you notice a difference before and after. Also how easy it is to do it yourself. I'm relatively handy but occasionally there is the "oops" factor.

Regards,
Tony.

[toc]

Just to let you know - the hyper tune kit arrived today. Have to say I think its a bit overpriced for what you get, but I guess if my mount becomes useable for AP, it will be worth the effort.

What's in the kit:
DVD (most important)
Sandpaper
4 new worm bearings
A collection of teflon washers
A collection of allen keys
A tool for removing the worm assembly
Screwdriver
Polishing compound

I've taken the mount apart - no big deal, but Im going to have to apply some heat to remove the collar on the worm assembly, as it is on extremely tight.

Ill keep everyone posted on my progress and outcome - I still have a few days left before I go back to work, so I can hypertune full time :)

[toc]

Here is some pictures of the kit - the DVD is not shown here.

[Tony_]

G'day Tim,

It doesn't look like much for $195 - but I guess the guy has to make a profit and it's easier than sourcing everything separately. What is the steel cylinder below the bearings?
I wonder if it will make much difference? - if it does I might go ahead with it too. I'm sure the parts can be sourced a lot cheaper - but it might not be that easy? Good luck with it.

Regards,
Tony.

[peter_4059]

Tony,

If you want to source the parts yourself it looks like they are the same as the EQ6 judging on the labels in the photos. Check out this thread:

http://www.iceinspace.com.au/forum/showpost.php?p=560248&postcount=32

Peter

[toc]

Well I just finished the hypertune! Not all that hard, just a bit of a pain. The hard part is getting the glued on worm gear locking rings, but a blow torch did the trick :)

To be honest I'm not sure what the point of all the calculations are to find the right teflon spacers - both RA and DEC ended up needing spacers that were about 10 times smaller than the smallest included one...

It does make a huge difference to how smoothly the mount works - balance is extremely sensitive now. The motors sound a bit different too, but that could be the placebo effect :)

I will find out if there is any difference to how well the mount performs for AP tomorrow night weather permitting :)

[toc]

That is a special tool that is used to help remove the worm collar. You could probably use different tool, but I was glad to have it, because removing the collar was hard enough :)

[Tony_]

Thanks Peter.
There is another kit available for about $US80 + postage (which is often ridiculously high from US) for the spacers, the bearings and lube.
The other bits in this kit are worth maybe $30? + the dvd (which is sold separately for $45). This kit is $US225 including postage, so that is about $AUD250. The kit is the easy way but it must be cheaper to buy the parts online.
There are a few videos on the net of how to do it - I might watch a few of these first. If it looks easy the $80 kit might be a good option. or just the spacers are $25. Apparently the bearings are readily available.
Apart from making the mount a bit smoother I wonder if it really helps PE and guiding much?

Regards,
Tony.

[Tony_]

Thanks Tim,

That tool is possibly an important part - I have seen how to make your own but sometimes its easier just to get one ready to go.
I'll be interested to see how it all turns out. All of the reports I have read have been positive. If it makes the motions and balance smoother it must also help PE and guiding?

Regards,
Tony.

[Tony_]

If the spacer you needed was 10x less - what did you use?

Tony.

[toc]

The thinnest one :) - thats what the DVD recommends - in fact he says you can forgo the spacer all together, but its better to have at least one bit of teflon there even if its a 0.3 mm rather than 0.03 mm. One that thin would get hacked up anyway probably.

[toc]

Well my CGEM didn't even track all that well (let alone guide) in the North because of some problems with the RA axis. That seems to have been rectified with smoothing and polishing the ring gear, so Im hopeful it will now work as advertised. Really I should have exchanged it a long time ago, but this last year has been when I've really tried some more serious AP, so Ive not noticed it until now.

[toc]

I think it will. Im not expecting miracles though - I'm still expecting a PE of around 15-20, and maximum unguided performance of around 30-60 seconds at 1000mm. If I can get that, and guide properly, I will be a happy camper :)

[Tony_]

I image at 2300mm - very difficult. Without guiding I'm lucky to get 30 sec exposures without the PE elongating the stars. The all star polar alignment seems quite good - sometimes I get virtually zero drift over a few hours.
Guiding is hit and miss - sometimes I can get round stars with 4 minute exposures (and probably more) - other times I get worse drift than if I don't guide. Possibly due to differential flexure or mechanical backlash.

Also since I got a cooled 40d camera I think I am pushing the weight limit once I piggyback an 80mm on my 9.25 SCT, with the camera on the 80mm. This will be improved with a well balance mount and maybe some improvements to the gear meshing and bearings.

It might be clear later tonight - I hope your mount shows some improvements.

Regards,
Tony.

[toc]

Gave the mount a try tonight, and managed to iron out a few more bugs and tweak the worm mesh. Hopefully tomorrow I can get some proper results - before adjustment I was noticing very strange behaviour, and PE of 100+ :eyepop: needless to say PHD couldnt cope :lol:

This is all part of the hypertune process - you spend as much time tweaking as the hypertune itself :)

[toc]

Had some more time to try out the scope tonight - definitely an improvement - my PEC seems to be just under 15 now. With only reasonable polar alignment, I can do unguided exposures of around 30-60 seconds at 1000mm. Not consistently, but better than pre-hypertune.

Guiding is still a no go though.

Ive tried every combination of setting you can think of, as well as trying the scope balanced, unbalanced to favour the weights, unbalanced to favour the scope, but PHD keeps losing control of RA, sometimes after only 15 seconds or so - Im actually getting better results by NOT guiding, so Im thinking the mount is not at fault.

I know others have had success with finder guiders but I don't seem to be one of them, so Im going to switch to my 80mm short tube and see how that goes.Anyway, another very frustrating night to be honest - I just with this damn thing would work :mad2:

[Tony_]

As long as there is little backlash and the balance is good then the guiding should work longer than 15 seconds - even if it drifts.
Maybe the guiding setting is too aggressive and it is oscillating in RA?

If the mount is moving smoothly then it is unlikely to be a mechanical problem - more likely guiding set-up or electronics?

I hope you sort out the problem - try the 80mm. I don't have much luck guiding. Sometimes it is near perfect - other times I get drift. I think it is caused by differential flexure. Do you have PEC turned on? I have read that it is best not to use PEC when guiding.

Good Luck!!

Regards,
Tony.

[peter_4059]

Tim,

Do you have the guide log enabled in phd? Viewing this can help understand what is going on.

[Tony_]

Can you use PHD to manually send adjustment commands to the mount to check that the correct signals are being sent?
Is it possible that the RA control autoguide has been reversed? If you are losing the guide star after only 15 seconds it may be guiding in the wrong direction? Even when I have forgotten to plug my autoguider into the mount head (stupid) it still takes several minutes to lose the guide star.

Regards,
Tony.

[toc]

Actually its not losing the guide star - it stays locked on, but the graph shows drift, and the images show oval stars.

The calibration step works fine, so I am assuming that the communication is working.

[Tony_]

Did you have this problem prior to the hypertune?
It happens to me most of the time - I have always thought it is caused by differential flexure, backlash or just ineffective guiding?
My biggest problem is trying to guide 2350mm fl with a 400mm fl guidescope and the nexguide which doesn't guide to sub-pixel. Sometimes it guides perfectly - other time I get drift.
Are the stars oval in any particular direction (RA or DEC) - that may give more clues.
I think I have read a report that the CGEM mount doesn't have good guiding in DEC the latest mc firmware is supposed to improve this?

Regard,
Tony.

[Rod771]

Tim and Tony

Which motor control firmware versions are currently running on your mounts?

You can download the MC update software here (http://www.celestron.com/c3/support3/index.php?_m=downloads&_a=viewdownload&downloaditemid=585&nav=0,7) if you don't already have it. 6.50 is the latest version which has the dec bug sorted.

Set the custom rate 9 setting (in the menu section) in the hand control to 4.00 degrees per second or lower if needed. CGEM users have have mixed results with 6.50 , Celestron suspect this could be due to different motherboards used during manufacturing. The main problem reported was heavy vibrations during high speed slews, setting the rate to 4.00 fixed this. It is also better to have more counter weight higher on the counter weight shaft than less weight lower.

When or if you update , definitely test the mount before loading it up with imaging gear to be safe , that's what I did anyway

I was able to get nice 10 min subs at 1960mm FL with OAG/Lodestar.

[Tony_]

I have the latest firmware. I think the guiding only uses much lower rates? - not the custom rate. Isn't that only for slewing or does using a lower slew speed improve the initial calibration?
The problem I have with guiding is that even when the guide star stays right on the middle of the crosshairs and the RA/DEC adjustments seem minimal, I get drift in the imaging scope. It doesn't happen everytime - but often enough. I have always though it to be caused by differential flexure or some other movement?

Regards,
Tony.

[Rod771]

Correct, I just wanted to make sure that in the case you had not had the latest firmware and then updated, that the custom rate was set to 4.00 to avoid reported vibrations :)


Sounds like flexure to me. Imaging at 2350mm you'd be better off looking into an OAG

Cheers

Rod

[toc]

Im running the latest. My DEC seems fine.

[Tony_]

Tim,

Have you had another chance to try out your mount?
Do you think the hypertune has made much difference - was it worth doing?

Regards,
Tony.