going prime focal

[Shiraz (Ray)]

You need to upgrade the focuser and get a camera adapter to make the scope work properly, whatever mount you have. Once you have the scope sorted out it should satisfy your imaging needs for many years to come, so it will not be wasted effort.

Suggest that you do not worry too much about the mount for now - until you get the the scope-camera combo tidied up, you will not be able to easily isolate possible mount problems.

In general though, your EQ5 is a bit lightweight for your scope and it will always have trouble tracking for long periods (although you may be able to make it perform significantly better with a tuneup). However, for now it is a good way to support the scope while you work on it and it will probably be fine for subs up to say 20 seconds - maybe more - if the wind is not blowing. And with a very sensitive camera like yours and an f5 scope, you can image a lot of interesting objects with short subs. Suggest that when you have had fun doing that for a while, you will know what the mount limitations are and you will also know where you want to go next.

[silv (Annette)]

I hear you, Shiraz.

But I can't just follow your thoughts.
Would I buy a focuser now, I would have to watch out for it's weight and possibly compromise in favor of a lighter focuser. (and pay more or miss out on features that a heavier focuser would have.)

I'll attach the test 30 secs to illustrate why.

Here, someone posted an image taken on a mount close to it's limit (and with properly mounted camera) and it shows the same feature as mine when I take shorter exposures that don't yet trail.

I'll attach also a stacked 8secs ISO 1600 version of NGC3247 - The Whirling Derwish - it's just good to know that DSS can make sense of the broken stars.

[silv (Annette)]

The 30 secs show 5 bumps instead of only 1.

I noticed that the zoomed live view enables me to do drift alignment (without having to buy a cross hair eye piece).
I will concentrate on that, following Octane's rule of 15.
Hopefully that will lead to a better tracking result and I can do another test shot to see whether the mount causes less bumps in 15 seconds exposures when it doesn't have to correct my poor alignment.
If I could even reach 20 seconds I would buy a focuser and go ahead with existing mount. If I can't - then I will buy a better mount straight away.

The EQ5 is said to be able to carry 9kg. That makes it 4.5kg in the real world. And the added motor already weighs what - 1kg?
omg. I wasn't aware of that.
This package was sold (without the motor) to the former owner (a visual astronomer) and I thought the setup would be working okay if a shop/a manufacturer sells this scope and this mount together.

[Shiraz (Ray)]

that is horrible tracking. Would have expected a lot better from the EQ5 - looks like there is some irregular friction or gear problem. Could probably be fixed with a tune-up, but you must be confident that you want to do this:
http://www.iceinspace.com.au/forum/a...p/t-17262.html

advice to date has been on getting what you have to work - however, if you are of a mind to upgrade, the question becomes what would be best. To some extent, you are heading down a blind alley with your current gear.

Starting from scratch, an entry level good quality astro imaging system based around your camera would probably be something like:
EQ6 mount (or HEQ5, but only if the EQ6 is too heavy for you)
ED80 scope or similar with field flattener and adapter for your camera
60-70 mm guide scope (or maybe OAG) with QHy5/Orion guide cam

You could decide to sell it as is, but your 8 inch scope would be a good addition to an ED80/EQ6 package - it would be right on the edge of the HEQ5 comfort zone though. You could fit a low cost GSO or Skywatcher focuser - should be OK for your lightweight camera and you will probably need an MPCC as well. If the upgrade to both scope and mount is too much for one step, you could tidy up the 8 inch scope and get a new mount for it.

there would be a market for the EQ5 and 8 inch scope - still fine for visual use.

would be nice to also get the opinions of refractor users on the best upgrade path.

[silv (Annette)]

cheers shiraz! I wouldn't dare to follow even those detailed instructions at this stage. my DIY skills are rudimentary - uhm, non-existant - I just don't think like a DIY person. (yet)

the previous owner has removed the chinese people's grease.
the mount moves really smooth when operated by hand during balancing.
the motor doesn't make any weird noise. no clicking, either.
he also fitted the GotoStar motor system. and he exchanged the 2ndary vanes with 2 circle ones.
all neat stuff I wouldn't be able to do myself.

I weighed the tube with all gear attached - 9kg.

[Shiraz (Ray)]

almost all mounts have periodic error due to imperfect mechanical drives - these errors cause wobble in the RA axis tracking and I suspect that is what you are seeing (if so, it is pretty erratic tracking). Your mount probably has errors something like
http://brough-astronomy.webs.com/app...toid=141221471 Thus, if you image over 5 minutes, you could produce stars that are smeared to about 50 arc seconds long in the RA direction (and maybe only 4 arc seconds wide). You can do 3 things to improve this:
1. image for short periods - if you image for 10-20 seconds, there will be periods when the RA rate error is small - you can keep these good subs and discard the rest. A photoshop add-in called star rounder can help tidy up slightly elongated stars
2. use PE correction - some mounts can be trained to put in small offsets to the drive to partially compensate for the known errors - don't know if your drive systems supports this and I have no experience with PEC.
3. add a second tracking scope (or alternatively off axis guider (OAG)) with its own camera that can track a star and feed corrections to the mount to compensate for the drive errors. (most people use this sort of system). However, I think your mount drive system will require an additional box to interface with the standard ST4 drive signals used by most tracking systems. Your system is already overweight, so this approach could be tricky.

Suggest an experiment to see how bad the drive system is. do your normal polar align and then deliberately offset the mount azimuth (not altitude) by enough to cause some gentle drift in the declination direction when you track a star near either the west or east horizon. Then do a single 10 minute image with the RA track operating - leave the dec drive fixed - the dec drift will allow you to see what the RA axis does - you should see a sort of sinewave formed by the PE cycle (I think this will work, although I have not tried it).

[silv (Annette)]

found the "blog" related to the periodic error graph you linked.

I feel I might understand the whole thing sometime - but I don't, yet. Can't even ask questions, that's how blurry it all is, for me.

How come, a guiding setup can reduce the mechanical errors? They do still occur: the gears are still too tight or some screws not holding something properly even.
(I'm not going to do auto guiding. Feels like cheating. Wanna do it the puristic way, first. But answering this question above would help me understand a bit more of the underlying problem, I hope.)

Read this thread about tuning a NEQ6. To get a bit of feel for ... something.

Then do a single 10 minute image with the RA track operating - leave the dec drive fixed - the dec drift will allow you to see what the RA axis does - you should see a sort of sinewave formed by the PE cycle.

"leave the dec drive fixed" - how would I do that? Connect the hand controller to the upper motor instead of the lower motor? (I assume they are both "motors" - both boxes have additional ports.)

What is it this 10 min exposure can tell me? A star trail that looks like a sinus curve?

2 of my nightly routines are:
* resetting PEC data in the controller (every setup is different in the alignment quality and if it is recording PE I don't want to use data from a previous setup.) I have no idea what the PEC really does. Apparently, the errors come from the motor wheels not being properly balanced and meshing into each other. How would PEC predict the next mechanical movement error and then how would it work against it? Slow the motor down or speed it up when approaching such a speed bump or a pot hole? (You wrote you don't use PEC. I'm just thinking loud.)

* sometimes using the "sync to target" option when the "select and slew" option has not put the object reasonably well within the FOV of the 40mm eyepiece. I will stop using this function, now, because I read somewhere that some controller software interpret this command as a "1 star alignment" and overwrite the sessions' 3 star alignment.
(Gotostar software is not well documented and outside support, anyway.)

[silv (Annette)]

I have pondered either buying a lightweight 80mm refractor or buying a new mount.
I can not tell whether my current newt has a parabolic or spherical mirror. (Eden Optics, 8" 1000mm f/5) There is no info anywhere on the internet. If it has a spherical mirror, the expense for a new refractor could be justified, regardless.
I can not tell whether the EQ5 has such severe problems that will be inherited by a lighter scope, too. I know, you wrote, the EQ5 will cope well with a scope half the weight. But I feel insecure, here. Not really understanding what the problem is - and risking that the expense for a new refractor will leave me moneyless when it turns out the mount is simply not good enough for even non-artistic, pure discovery AP like I want to do.

I bought a GSO crayford focuser and am awaiting the t-minus adapter.
I doubt the focuser will dampen the bumps. But I will give it a try, anyway.
I will also see what happens with tracking stars close to the eastern, northern horizon (I don't have a southern or western horizon due to forest) or high up at the zenith.
And I will try and have more weight at the east for every different object as I read that this might help the motor, too. (I didn't understand the reason, though.)

It's likely that the tracking errors are insufferable for me.

I made a brave decision: I will take the mount apart.

I am currently looking for a new profession and was actually considering going into something more to do with my hands. Life is short and I've never worked with my hands, before. Would be a shame not to try that before I die.
Instead of making a profession of it (weird, how I still regard my jobs as my prime source for passion, fun and fascination) - and who would train a 45 yr old female, anyway - I could realize it with this project. Will be tough I reckon. I only have my small bed room. Only the desk can hold all the parts while I'm working on them for quite a while. And doing it without any guidance and knowledge - nor understanding yet all the English terms (e.g. what's a "worm gear"...) is an ... adventure.
But taking this diversion from the straight path has its merits for me, personally. Letting go of the desired goal "AP" for a while and embracing the opportunity at hand. It's also a spiritual practice, probably bringing my soul closer to Nirvana

ZeroID, in case you read this: I would not want to occupy your work room, in case you are about to renew your offer.
I understand it will be a project that will take a few long sessions, possibly even including wait time for spare parts. I want to be able to work on it whenever possible and not feel I might become a nuisance to you.

[Shiraz (Ray)]

Mechanical errors arise because it is just not possible to make gears etc with the extreme accuracy required for near perfect tracking. The gear and bearing tolerances need to be maybe 1/100 the width of a human hair to get fine tracking and no readily affordable system is that good. Guiding with a second scope overcomes the effects of the mechanical errors (which are unavoidable) by adjusting the tracking speed to compensate for any drift in a star being imaged by the guide scope - eg if the star being guided on moves ahead on the guide scope camera, the guide software effectively tells the mount to slow down a bit - and vice versa. In a perfect system, if the star can be made to stay in the same place in the guide scope, the images taken by the main scope will stay as points as well. The mount still needs to track smoothly though for this to work properly and EQ5s are pretty jerky. Even the $10k+ crowd use guiding to tidy up mount tracking inaccuracies.

When doing the suggested 10 minute test, just set the mount tracking normally and don't touch the Dec or RA adjustment buttons. For a 10 minute long exposure, I guess you use the bulb setting on the camera and leave the shutter open for 10 minutes. The test will show you how rough the tracking is. It is pretty hard to assess just what your mount is doing without some form of test results that we can measure.

If you have no idea what PEC really does, then turn it off if your mount software will let you. PEC has the potential to mess things up if not done right and you might improve the mount by disabling it. Only use it when you understand it. What process do you go through to train PEC at present?

Don't know the brand, but I would be surprised if your scope has a spherical mirror - maybe the original owner could help. When you have installed the focuser, I would hope that you will have a pretty good scope.

It is a really brave decision to dis-assemble your mount if you are not confident, especially if someone else has already cleaned it up. Your call, but suggest that before you do a full pull down, you work out how to adjust the RA and Dec worm clearances to minimise slop in that part of the gear-train. This could possibly improve your mount by quite a bit without too much risk and there are video tutorials that should help you. EDIT: just found this in your other thread - you should definitely adjust the worm gears. whereas before, pushing the left-right-up-down buttons almost immediately reacted and moved the scope into that direction,
tonight, the scope first performed a tiny backwards circle before it then "found" the direction it should move to.

My overall advice is still to get the scope and camera working OK and then start on the mount. Then get the mount working as well as possible and do some unguided imaging with short exposure subs. Getting good results from imperfect components can be a satisfying art form in its own right. Once you have done enough imaging to know what the true capabilities and limitations of the mount and the scope are, you will have a fair idea of where you want to go next - and that will almost certainly include a better mount. have a look through the show and tell forum - lots of scopes that look a bit like yours, but on heavier mounts. eg http://www.iceinspace.com.au/forum/a...se.php?a=66197

since this thread is becoming more about the mount, suggest that it might be a good time to start up an EQ5 performance thread and tap into the knowledge of those who have used that system.

[Screwdriverone (Chris)]

Hey Silv,

What sort of 8" newt do you have?

I solved my in-focus issues by buying one of these for my Skywatcher 8" F5 newt, I still have about 12mm of inward focus travel with this baby in. I tried the mirror springs and screws and the slop in the primary (it leant over) was so bad the coma was horrible.

Works for me, not sure if you have a Skywatcher or not.

http://modernastronomy.com/accessories.html Scroll down to 2" Adapter with Compression Ring - for SkyWatcher Newtonians with M54 thread.

Hope this helps (or at least shows you how to solve the problem on your scope)

Cheers

Chris

[ZeroID (Brent)]

Silv, good on you for wanting to get stuck into the project but I suspect you might be biting off a bit more than you think pulling it all to bits if you don't have a good idea as to what you are looking for.
You might do better getting some help in your setup to see what else is going on. Balance, alignment and loading may be a large part of your problems at present that someone would be able to point out without stripping and rebuilding unnecessarily.
I'd suggest going along to one of the Auckland Observatories evening sessions and having a chat to someone there. Hopefully they can show you some solutions.
I don't think Nirvana is found pulling mounts apart.
I have quite a large garage btw so a bit of space would not have been a problem.