oymd

1 minute ago, globular said:

Looks like you might not have defocussed quite enough.  And you should do it both inside and outside of focus.

Oh, I did not know that...so I should de-focus in both directions then?

I did defocus all the way out, but I never say a doughnut similar to the one you kindly provided in your image. It went from a doughnut to completely disappearing. I used my camera and PC.

Is it a pre-requisite to collimate using an EYE PIECE rather than PC and camera?

17 minutes ago, Peter Drew said:

It looks "ok" at a glance but it is far too out of focus to give a definitive assessment.  You need very high power and almost focussed to accurately judge the collimation.     🙂

Thank you Peter fr your reply

I am using a camera and the PC for the collimation.

Can you please clarify what you meant by "very high power" and "almost focussed"?

If the star is almost focussed, it would be tiny and pinpoint on the screen, and I would not have a doughnut?

Apologies, I am new to this, and I do not follow?

With galaxy season upon us, I've decided to give my C8 a go.

The OTA is 2 years old, very lightly used and I had never collimated it before.

To check that my collimation is ok, I used NINA to slew to a bright star, plate solved and centred, then I moved the electronic focuser out of focus.

I could see the doughnut and it looked centred to me, so I left it alone.

Am I missing something, or does it look ok?

Is that all I need to check regarding collimation?

Many thanks

3 hours ago, vlaiv said:

There are two sources of backlash in HEQ5/EQ6 drive mechanism.

First is motor gear part which is replaced by belt mod and second is worm / worm gear engagement that can be tuned out to some extent.

Belt mod removes that first source but does nothing to the second.

Ideally if you want to completely remove backlash - you'd need another mod. You would need to add spring load or magnetic load to worm/worm gear engagement.

With my HEQ5, I can't completely tune out worm/worm gear backlash because worm gear seems to be not quite circular but squished a bit. If I tune it at one point - it will either bind or have some play at 90 degrees to that. This happens both in RA and DEC - but I've found a way around it.

For RA it is not as important if you preload your mount properly (just a bit preload is needed - a bit of east heavy) - that backlash is far from drive gear and guide corrections won't disturb it. 

With DEC, I can't use above trick as it is not constantly moving, but there is another trick. As backlash depends on the part of the circle - I just setup DEC in such way (using clutches and rotating the ota in DEC) so that I'm at good part of the circle without issues for duration of the session (gets tricky when there is meridian flip as DEC turns for 180 degrees - but if error is equal - you should land on good section again).

HI Vlaiv

What do you mean by East heavy? And by how much should I be out of balance?

On 13/02/2023 at 21:41, vlaiv said:

By the way - I would not get 10 micron mount for myself (although it might look like I'm the fan from above discussion).

It is indeed pricey in my opinion - and I would not have use for it.

I like friction mounts better, and I'm actually eyeballing this one:

https://www.geminitelescope.com/efric-friction-drive-mount-german-equatorial/

@vlaiv

Apologies, a bit off topic here.

I am also very interested in the Gemini e-Fric, but with the sad news of Andreas passing away a while back, is the mount still in production and supported?

21 hours ago, FLO said:

This Starfield Herschel Solar Wedge has all the features and performance associated with a modern Herschel wedge:

• Herschel optical system
• Suitable for visual and imaging
• Fully multicoated optics
• CNC-machined chassis
• Adjustable brightness
• Ceramic heat tile
• Twist-lock accessory holder
• Translucent diffuser for centring Sun

And an attractive price 🙂

Starfield 2" Herschel Solar Wedge V2

 

Would this be a good option for imaging?

6 hours ago, MikeBY said:

You cannot put a focuser between the reducer or telescope and camera.  You mess up the backfocus..

Good morning

Sorry, I am not following?

The Esatto 2" focuser has been widely used with the EDGEHD scopes and the reducer?

I'll be immensely grateful if someone can advise on this imaging train.

After experimenting with imaging with the Edge HD, mirror flop and shift, I decided to by pass the issue entirely, and LOCK the mirrors, hence purchasing the Esatto.

Can you please recommend which adaptor will be used on the CAMERA side? And how to reach correct back focus of 146mm?

The OAG I am using is the newer OAG-L, with the 12x12mm prism and 48mm aperture.

Camera is the 2600MM mated to the 2" EFW.

Here's my imaging train:

TWO OPTIONS. One WITH, and one WITHOUT 0.7X Celestron reducer.

EdgeHD 11 ===> 0.7X Reducer ===> Esatto 3.3" adaptor ===> Esatto 2" Focuser ===> ?? ===> ZWO OAG-L  ===> ZWO 2" EFW ===> ZWO 2600MM Pro

EdgeHD 11 ===> Esatto 3.3" adaptor ===> Esatto 2" Focuser ===> ?? ===> ZWO OAG-L ===> ZWO 2" EFW ===> ZWO 2600MM Pro

Many thanks

10 hours ago, vlaiv said:

What is your guide exposure (how long is it)?

Try the following:

Shoot one or several subs with your regular guiding settings and then use longer guide exposure - like at least 4 seconds and shoot another set of subs.

Compare FWHM values between two sets of subs.

If there is no significant FWHM difference (or even FWHM or second batch is smaller) but RMS got down - then it is the seeing that is at fault.

I’ve experimented with various guide exposures. 
 

On my AZ-EQ6 I found 2 seconds to be perfect. 
 

With this CEM40, anything over 1s, and tge RMS shoots up and PHD2 turns into an ECG of a patient with atrial fibrillation!!

But that is just by viewing the graph. I should try comparing FWHM as you suggest!

16 minutes ago, vlaiv said:

Can't really see well on that video - is the whole mount (or rather RA part) moving when you push on CW bar or is it just CW bar?

In any case - that's not looking good - there should be no wobble like that and I don't think it is caused by springs in spring loaded worm. That motion is "perpendicular" to springs themselves and should not be related to them.

its when I wobble the CW bar to the left, the Scope and everything on it wobbles to the right, and vice versa. Its barely visible, but can be felt very easily.

Tightening the worm/gear mesh eliminates it, but then locks cannot be released

52 minutes ago, vlaiv said:

Ok, so if you are using iOptron commander - it is different from using EQMod.

You won't be doing PE curve preparation - mount will do that for you, or rather iOptron commander will do that for you. In this case - it must know what the needed corrections are and you need to start guiding when you hit PEC record. Commander will track where mount is supposed to be - but it will also track corrections and from the two will derive PEC curve.

You need to keep it like that for at least couple of PE cycles - let's say 5 cycles - that is 2000 seconds total, so just a bit more than half an hour.

Once you are done - when you next start RA tracking, regardless if you are guiding or not - you can hit PEC playback and it will apply recorded correction to the mount. It should keep that PE correction until you record a new one - so you should be able to reuse it very session by playing it back.

As far as 1.2" RMS - that is quite a lot, and there are couple of things that you should look into:

1. Do above advice on balancing your setup

2. See if your clamping connection is strong enough for the scope - you might need to improve that

3. You should have virtually zero backlash since you have spring loaded gears - make sure you've tuned that properly in both axis

4. Make sure your tripod is sturdy enough and have been placed on ground where it can't move - don't put it on soft ground like sand - or if you do - try to "dig it in" a bit so it is rock solid. If it has extending legs - don't extend them fully - you don't need your setup to be at "observing" position for imaging. It can be lower than that.

1 hour ago, drjolo said:

These spring loaded CEM40, CEM26 and similar mounts are very susceptible to perfect balancing - in RA, Dec, but also along the telescope axis. So if you have heavy focuser motor or guide scope on the side, it needs to be balanced on the opposite side of the OTA. Worm gear tension needs to be adjusted as light as possible to cancel the play, but no more. Stepper motors in these mounts are undersized and such behavior may be a reason of accumulation of microsteps that are released after some time. 

And this is what I meant by the RA wobble

58 minutes ago, drjolo said:

These spring loaded CEM40, CEM26 and similar mounts are very susceptible to perfect balancing - in RA, Dec, but also along the telescope axis. So if you have heavy focuser motor or guide scope on the side, it needs to be balanced on the opposite side of the OTA. Worm gear tension needs to be adjusted as light as possible to cancel the play, but no more. Stepper motors in these mounts are undersized and such behavior may be a reason of accumulation of microsteps that are released after some time. 

40 minutes ago, vlaiv said:

Ok, so if you are using iOptron commander - it is different from using EQMod.

You won't be doing PE curve preparation - mount will do that for you, or rather iOptron commander will do that for you. In this case - it must know what the needed corrections are and you need to start guiding when you hit PEC record. Commander will track where mount is supposed to be - but it will also track corrections and from the two will derive PEC curve.

You need to keep it like that for at least couple of PE cycles - let's say 5 cycles - that is 2000 seconds total, so just a bit more than half an hour.

Once you are done - when you next start RA tracking, regardless if you are guiding or not - you can hit PEC playback and it will apply recorded correction to the mount. It should keep that PE correction until you record a new one - so you should be able to reuse it very session by playing it back.

As far as 1.2" RMS - that is quite a lot, and there are couple of things that you should look into:

1. Do above advice on balancing your setup

2. See if your clamping connection is strong enough for the scope - you might need to improve that

3. You should have virtually zero backlash since you have spring loaded gears - make sure you've tuned that properly in both axis

4. Make sure your tripod is sturdy enough and have been placed on ground where it can't move - don't put it on soft ground like sand - or if you do - try to "dig it in" a bit so it is rock solid. If it has extending legs - don't extend them fully - you don't need your setup to be at "observing" position for imaging. It can be lower than that.

Thank you so much for your prompt responses

1- With regards to BALANCING, i can say with confidence that it is PERFECTLY balanced. Too balanced in fact. As the ZWO EAF sticks out too much on one side, I attached a short WO dovetail on the opposite side, and loaded it with washers to achieve perfect balance in the third axis. Balancing these CEM mounts is ridiculous! Attached is a pic showing my DIY counter weight for the focuser and my latest calibration after stripping the mount and replacing the belts.

2- everything seems to be RIGID

3- DEC has no obvious backlash. RA has a VERY slight ROCKING/WOBBLE when I manually push the counterweight to one side. IT IS IMPOSSIBLE TO GET RID OF IT. The only way I can get the RA to be solid with ZERO wobble, is to tighten the gear/worm meshing to the point that I can no longer undo the RA lock and I get stiction. Even if I then loosen the meshing by 1/1000th of a turn (exaggeration here of course ), the RA wobble immediately comes back. There is simply no sweet spot where the gear/worm meshing eliminates the wobble, yet can be unlocked and slews normally. I have spent DAYS on this!

4- Tripod is the beefy 2" one, with legs all the way in, and on concrete floor.

Sorry to intrude on the thread, but I want to understand PEC recording and how to apply it to my mount.

I am troubleshooting my CEM40, which seems to behave badly in RA, immediately as I start PHD2. It jumps to RMS 1.5 in a matter of 1-2 seconds, NO MATTER WHAT I DO.

Mechanically I stripped the mount, changed the belts, have the bearings on order, but still the same behavior.

Tried fine tuning the mesh binding between the worm and gear, improved the DEC backlash significantly from >65000ms to about 400ms, get good PHD2 CALIBRATION results, but RA is hopeless. Never better than 1.2RMS

With regards to PEC recording and applying, what should I do?

In IOPTRON Commander, there is the option to RECORD PE.

There is also an option to PLAY BACK the PE.

When, how and how long do I PLAYBACK the PEC?

From the above, my understanding is to record PE when the mount IS NOT GUIDING or connected to PHD2?

My work period is 400s, but in PHD2 it auto corrects to about 800s, when I choose the PPEC alogorithm for RA guiding

@vlaiv

Vlaiv, would be great if you can help me with this?

How to I apply the PEC that I record in Ioptron Commander to my mount's guiding?

I've run the PEC recording while guiding, whoile NOT guiding, with PHD2 closed, and it seems to give me random results.

I do not have PEMPRO, which I read that is needed for applying PEC recording to the mount's guiding?

Imaging is at 350fl, 294MC Pro had 4,63micron pixels, so imaging scale is 2.7"/pixel.

Starts are more or less round, and I am actually surprised that the subs look much better than what you would expect when ;looking at the graphy on PHD2, but I know something is wrong.

Guide scope is the SW Evoguide, 242FL, camera is 120MM Mini 3.75micron, so guiding at 3.2"/pixel

Sorry, so so confused?

12 hours ago, Stu said:

Ossi, the simplest way would be to use it with a Daystar Quark ‘eyepiece’ filter’

1 hour ago, Peter Drew said:

Easiest way is using a Herschel wedge for "white light" for sunspots etc, or as Stu says, a Quark for H-alpha.  The cheapest conversion is a front mounted solar film filter for white light only.  Slippery slope financially!   🙂 

Thank you both for your advice!

"Slippery slope financially"

Show me something that ISN'T a slippery financial slope in this crazy hobby!

So, my point is, using any of your two suggestions, will that allow mw to properly image the sun, or it will be some kind of bad basic compromise?

They seem to be very expensive options, so want to know if any of them will work well, and give me good solar imaging options?

I realise that the high end solar scopes are £££, and I am realisitic. I am not aiming for that.

Just a good solar scope for visual, and more importantly some basic imaging. (still do not fully understand solar imaging, but I hope I can get YELLOW images of the sun, not just the basic white/grayscale)

Many thanks

Ossi

Hello everyone!

My first telescope in the hobby was a SW 80ED Pro that I bought from FLO as a kit 2 years ago. 
 

After only 2 months of using it I upgraded to all sorts of equipment and telescopes and have not used it since and it has been sat in it’s aluminium box ever since. I do not want to sell it, and would like to convert it to a solar scope. 
 

I’m keen into getting a taste of solar imaging, but I find the necessary kit a bit confusing. 
 

Is it possible to use said telescope with some appropriate H Alpha filters as a solar imaging scope?

Many thanks

Ossi

8 hours ago, vlaiv said:

I don't think it is tilt, but I do believe it is some sort of collimation issue - maybe decentered lens or something like that.

Here we have two stars in R, G and B channel - and they have different size and shape.

I can't be sure how much of it is down to stacking (we need simple average stack to check that) and how much is down to optics.

This pattern repeats over the whole image and is not prominent in one corner so I don't think it is tilt issue. Fact that colors are affected differently suggests that something is going on with lens. There might be some spherochromatism or something like that. This flaring that is most obvious in red is also very interesting. It looks like some sort of obstruction is present, but I have no idea what it might be.

First thing that I would recommend would be loosing the filter and trying to image simple star field to see if this would repeat.

Well, actually - first thing to do is to stack using regular average stacking to see if there will be any difference to this stack, and second - loosing filter.

Third thing to do would be to image star in/out of focus to check collimation and perform sort of star test in general.

Here is the stacked TIFF file from DSS.

Under the LIGHTS tab, I left it at default, which was AVERAGE.

Everything else was also left at default.

WOW, DSS completed the whole process in under 5 minutes!!

WBPP took about 20 minutes, if not more!!

Autosave.tif

8 hours ago, vlaiv said:

I don't think it is tilt, but I do believe it is some sort of collimation issue - maybe decentered lens or something like that.

Here we have two stars in R, G and B channel - and they have different size and shape.

I can't be sure how much of it is down to stacking (we need simple average stack to check that) and how much is down to optics.

This pattern repeats over the whole image and is not prominent in one corner so I don't think it is tilt issue. Fact that colors are affected differently suggests that something is going on with lens. There might be some spherochromatism or something like that. This flaring that is most obvious in red is also very interesting. It looks like some sort of obstruction is present, but I have no idea what it might be.

First thing that I would recommend would be loosing the filter and trying to image simple star field to see if this would repeat.

Well, actually - first thing to do is to stack using regular average stacking to see if there will be any difference to this stack, and second - loosing filter.

Third thing to do would be to image star in/out of focus to check collimation and perform sort of star test in general.

I recall from our previous conversations that you use DSS. 

I will restack the subs in DSS. I haven’t used DSS for a while. 
 

What sort of parameters do you advise to use in DSS to avoid any rejection and keep it simple as you suggest?

29 minutes ago, vlaiv said:

@oymd

Could you restack your data but using simple average method without fancy things like rejection and such? I think that strange effect might be caused by guiding issues and strange stacking settings.

Also, if you can - post fits of stack, xisf is PixInsight only format

Hi Vlaiv

Master saved as FITS and uploaded!

Thanks

11 minutes ago, vlaiv said:

Yep, that would be great.

Do you know how to do it manually? Just calibrate, align and use simplest integration method - average without any weighing of subs or pixel rejection

I'll try and do that.

As I am writing this, I am actually uploading the Master Light in FITS format for your consideration

masterLight_BIN-1_4144x2822_EXPOSURE-300.00s_FILTER-NoFilter_RGB_autocrop.fit

8 minutes ago, vlaiv said:

@oymd

Could you restack your data but using simple average method without fancy things like rejection and such? I think that strange effect might be caused by guiding issues and strange stacking settings.

Also, if you can - post fits of stack, xisf is PixInsight only format

HI Vlaiv

I do not touch anything in the stacking process.

I use WBPP. Load masters dark and flat, and load all the lights.

I then stack using the default WBPP settings, and do not touch anything.

Can I save the master light as a FIT and post it here?

2 hours ago, PadrePeace said:

Please could you post the whole field of view?

You state the temp was +15C during capture so not obviously the atmospheric conditions. Never seen stars look like this from a guiding issue.

You suggest that the scope is permanently set up on a mount and has just started having issues. If that assumption is true then it’s not likely an impact symptom or a temperature conditioning issue as it will always be ambient.
Please confirm both assumptions. Just covering off some missing context of use.

To my eyes: the larger stars to the left of frame show three extended bright arms in the corona. Hard to tell how smaller stars are impacted. Curiously, this pattern changes to bottom right of the example frame (assumed to be a single sub) similar to a ‘coma’ look (which should not be possible in a refractor) but which suggests focus is changing across the FOV.

SO WHAT?

Check if the optics are clear of obstructions internally and externally ie bugs spider web threads; has a baffle moved?

Have you got an additional dew shield fitted that might now be impacting the light path?

Were you imaging through branches of a tree or similar distant obstruction which may give you weird stars?

Did this issue happen on all subs, ie over a prolonged session? 

What about with other filters in the optical path?

I’m not an expert but offer some less technical questions to address before you try dismantling the scope!!! Things seldom just break if not abused so look for the less obvious possibilities. 

Hope this helps.

 

 

2 hours ago, vlaiv said:

Yes, still linear sub would be great to examine.

What sort of filter was this shot with? Was any filter used at all?

I've seen strange stars like this when no filter is placed on refracting optics. It is usually due to out of focus IR/UV light.

1 hour ago, Peter Drew said:

Change of focus or shapes across the field of an image is usually the result of tilt either in the optics of the telescope or any supplementary optical components including the camera.  My money is still on tilt somewhere in the system.    🙂  

All conditions and gear used provided, and uploaded subs and master light.

Many thanks for your help.

Thank you all for your replies.

I've attached a THREE subs, one at the start of the session, one in the middle and the third close to the end.

Also attached the Master LIGHT.

The gear used was:

WO71 Apo, 350fl

ASI294MC Pro

CEM40

Optolong L-eXtreme filter

Ambient temps at night are 15C.

Optics on telescope, filter and sensor window are pristine.

No obstruction what so ever.

Total 69 subs x 300s.

Calibrated with Master flat and master dark

masterLight_BIN-1_4144x2822_EXPOSURE-300.00s_FILTER-NoFilter_RGB_autocrop.xisf 2023-01-05_20-01-44__-4.90_300.00s_0001.fits 2023-01-05_21-48-51__-5.30_300.00s_0020.fits 2023-01-05_23-19-44__-4.90_300.00s_0003.fits

2 hours ago, Adam J said:

It looks like pinched optics, its the only way you will get star shapes like that. Its not tilt as that would not notch out the star halo like this. If its not happened before was it very cold when you collected this data?

Adam

1 hour ago, Rodd said:

Almost looks like a guiding or periodic error issue.  There is a side to side elongation.  I hope you figure it out.  These kind of issues are really annoying, especially with a quality scope.

I’ve just watched a video on YouTube by Lukomatico. 
 

The video is a review of the Askar 130 APO, and I noticed in his video he had a problem with the matching reducer. His target is similar to mine, IC1805. 
 

He also shows similar UFO shaped stars. Specifically at 13:40 in the video. 
 

He describes it as Tangential and Saggital astigmatism. 
 

Could it be astigmatism?

@vlaiv Wish you can give us your opinion on this!!???

1 hour ago, Rodd said:

Almost looks like a guiding or periodic error issue.  There is a side to side elongation.  I hope you figure it out.  These kind of issues are really annoying, especially with a quality scope.

Guiding overall is not great. About 0.8rms on the CEM40. 
 

How can I trouble shoot this?

2 hours ago, Adam J said:

It looks like pinched optics, its the only way you will get star shapes like that. Its not tilt as that would not notch out the star halo like this. If its not happened before was it very cold when you collected this data?

Adam

Ambient temps are about 15C at night. 
I thought pinched optics happen only in very cold weather?

Could it be too much heat from the dew straps?