symmetal

@900SL. No problem. I'll make the spreadsheet. I get all the info needed from the curves published by Zwo. I'll use the offset/bias figures you've quoted for an image you can download. I'll give a link to download the excel file too so you can make any changes you want to print your own sheet.

The formula used is on the third line of the image I posted. Vlaiv provided the formula as an improvement on the one I originally used and he approved the latest spreadsheet contents too when I last posted it. 😊

The gain value used is the e-/ADU figire of course and not the camera gain in 0.1dB steps.

I can use the data provided by @ONIKKINEN to provide another sheet using actual values to see how it compares to the published specs.

Alan

@BrendanC I've produced Excel sheets for some cameras giving exposure times for specified read noise swamping factors like this. If you wish I can make one for the ASI533. You just need to input your mean bias ADU value ( and camera bit depth if not 16 bit) and optimun sky background ADU values are calculated. Swamping factor 5 is what I use, as vlaiv has recommended this in the past. With the calculator top right you can get an exposure time for a specified background ADU by inputing the values from a test exposure, or a previous sub you've taken if the sky darkness is similar.

I also use zero gain when using luminance filters with the RASA 11 as at gain 100, it will swamp the read noise in 15 seconds, (in bortle 3). At gain 0, around 60 secs is required which is better to avoid 100s of subs.

Alan

Hope you don't mind me posting it here Göran, but my 2 hours of imaging was spoiled by high thin clouds passing through which played havoc with the flats calibration. Only the first 5 subs were reasonable before the Moon got too high as well and washed everything out, so I thought I'd see what 5 mins with the RASA 11 would achieve. 😁

5 x 60s L-3, ASI6200MM gain 0, RASA 11, full Moon 🙂

I think there's a bit more detail visible in parts of M81 and M82, than on yours Göran. 😁 620mm fl may help too.

If given more stretching the IFN does becomes visible.

Alan

That's quite a difference Göran. Thanks for posting.

By coincidence, I happened to image the same area last night with the RASA 11. The Moon was full so was going to pur the 2600 on as there's not much Ha around this time of year, until I realised I'd only bought the M54 adapter for the Baader UFC system. Until I get the M42 adapter I can only use the 6200 and so with the Astronomik L3 pointed it at Bode's galaxy as it was well away from the Moon, in the hope of getting some IFN. I got 2 hours of 60s exposures at zero gain before the high clouds got too much. Will see how it turns out later. If it's any good you could add it to your image. 😀

Alan

If you had previously plate solved before manually moving the mount then plate solving again will end up with two sync points that don't correspond with a valid map of the sky as the mount is unaware of how much it was moved manually. The mount just computes the number of stepper motor pulses to apply to go from one location to another. This will likely affect the home command too so it will not return to the correct home position. Doing a Park and Unpark should remove any sync points I would expect, or else it wouldn't fix the problem.

If you haven't plate solved before manually moving the mount, then plate solving after moving should be OK. The mount knows the RA and Dec coords at the home position, so can work out how many steps are needed to get there from the plate solve. You can easily check this by doing a home command after this first plate solve after manually moving, and check it does in fact go home correctly.

It found M101 correctly for your first session, but how far off was the initial slew before it had to do more plate solves and slews to get correctly on target. If your flip hadn't ended up near the pole, then it may have completed the flip correctly with a few more target centreing slews and you wouldn't have known there was an issue. I don't know how far ASIAir will allow a first slew to be off target before it aborts any further slews. I use SGP with ASTAP plate solving, and SGP can report a failure and halt if the first slew is too far off target.

Alan

19 hours ago, CraigD1986 said:

Cone to think of it, when I was setting up, I polar aligned, slewed to M101 and then released the RA clutch, rotated the mount to check for collisions with the back of the scope. Then when I went to slew to M101 again via SkyView on ASIAir, everything was way off, including when I told the mount to go home. I then manually pointed at Polaris, plate solved and pressed “sync to mount”. Then I slewed to M101 successfully and began imaging. I wonder if something was out at this point, causing the incorrect position after the flip?

Releasing the clutch and rotating the mount manually will make it lose knowledge of where it's pointing. As far as the mount's concerned it's still pointing at M101. The AZ-EQ6 has encoders on each axis which will tell it if it's been moved manually, but the EQ6-R doesn't. When you went to re-slew to M101 it likely didn't move much as it thought it was already pointing at it. Hence it would be way off when you homed it, as it thought it was homing from being pointing at M101.

Using Polaris to plate solve is not recommended for an eq mount, as unless your polar alignment is spot on, as it will likely give a RA position thet is significantly off being correct, because the RA hour lines are very close together near the pole. If you're pointing at the pole itself, any random RA position will be correct.

I don't know if the ASIair keeps an internal sky map of its sync points to assist with slewing if your polar alignment is not perfect, similar to what a two or three star alignment does. If it has sync points for M101 and an incorrect Polaris it would make the position after the flip, off to some amount, but unlikely to be as far off as you had. It's only because you unfortunately ended up near the pole it wouldn't accept the plate solve as being accurate, so wouldn't then continue slewing to the correct position of M101.

EQMod has an annoying feature where it will maintain the previous sync points between sessions, and you have to manually delete them at the start of each session, or your slews will likely be off and it can sometimes never centre to the correct position.  If plate solving is used, keeping a sync point map is not a benefit. I assume ASIair doesn't keep sync points between sessions so this shouldn't be an issue for you. 🙂

Alan

This article from Harvard University may help.

THE HUMAN BODY IN SPACE: DISTINGUISHING FACT FROM FICTION

Alan

It seems the mount, for some reason, stopped moving in RA and Dec at about the same time half way through completing the flip. As it ended up near the pole the sync was not performed after the plate solve as it's known the result would not be accurate. The ASIAir seemed to assume it an error in syncing, and ignored it, and declared this as a flip completed, so started imaging again. Every few minutes later, presumably before each new exposure, the mount  is commanded to slew to the new target position again as the ASIAir presumably hasn't had confirmation that it is on target. The mount doesn't actually move at all each time so the same response is given and the process just repeats. 

It looks like the mount shut off power to the motors mid way through the flip due to some failure detected, possibly power related, and never restored motor power. A sudden increase in current drawn, due to the scope being prevented from moving, by hittting the tripod or a cable snag may cause the mount to enter a fail safe mode where a repower is needed to reset it.

Alan

On 31/03/2023 at 06:44, Jeffrey Johnson said:

I just now found the key to success on this:

Instead of the *latest* ASCOM driver (ZWO_ASCOM_Setup_V6.5.6)

For XP use this one:  ZWO_ASI_Camera_ASCOM_6.5.1   (thanks again Alan for providing this!)

V6.5.1 instead of V6.5.6!  (V6.5.6 does work for Win7 32-bit, however...just not XP)

Jeff

Glad to hear you've got it all working now Jeff and that some of my files were useful. 🙂 The later Ascom drivers include the EFW driver so it's not needed as a separate program, but it looks like it doesn't mind having them both installed.

Alan

@michael8554 Mine is an EQ8-R which is different from the EQ8 arrangement with better tension adjustment. Belt condition and alignment looks good, though I'm wondering if the tension could be tighter. Only modest effort is needed to rotate the belt through 90 degrees or depress it as shown. The tension adjustment screws are tight so it hasn't slipped. On my AZ-EQ6 the belts were very tight with no real belt deflection available, which I thought could be too tight but it doesn't seem to cause problems. Do you think it should be tighter?

On car timing belts, 90 degree flex on the longest run is standard I believe, but that's over a much longer distance than this. 

Alan

2 hours ago, michael8554 said:

Tension yes but also misaligned pulleys, damage to belt.

Michael

Ah! OK thanks. I'll check when the weather improves. 😉

Alan

6 hours ago, michael8554 said:

So you're discounting the RA belt drive ?

Sorry I didn't refer to the belt drive. I assume you're implying that the belt tension may need adjustment. This webpage has some good pictures of the EQ8 and it looks like the block the stepper is attached to has a tension adjust mounting screw as shown.

I'll take the cover off and have a look. Not knowing what the correct tension feels like, it may be a case of trial and error, but worth checking if the problem persists.

Alan

@michael8554, thanks for your assessment. As you say it's not enough to account for the star trailing. There is Dec backlash but this doesn't affect imaging much, and is only apparent when a dither move has moved it to the other side and it takes a while to take up the backlash as shown at the end of the East run. When I first got the mount it sometimes didn't return fully to the home position in RA when parking so there was likely some binding but that doesn't happen now. I've monitored the current doing fast and slow slews from side to side with no significant changes.

Unfortunately it will be at least a week before the weather might improve and I can try again.

Alan  

9 hours ago, michael8554 said:

Hi Alan

The guidescope mounting is much better than the commonly used soft-tippped screws in rings.

Maybe good enough to discount diff flex from that source.

In each 10 minute guided runs, were the RA and Dec guide figures similar to each other ?

That suggests guiding was good enough to give round stars,

Leaving only gravity related movement elsewhere.

Michael

Hi Michael,

I thought I'd better analyse the guide logs and they indicate poorer results than were evident looking at the live trace, but not bad enough to give the trailing visible. Image scale is 1.5"/pixel. The south facing trails are around 6 pixels long which implies 9" total movement and equally bright over most of their width. The periodic error suggests 2" spread over like 98% of the imaging run. The odd spikes in RA looking South need looking at. Maybe a bit less East heavy needed as the East imaging shows less RA spikes when the weights were near vertical. Seems I need to increase RA agression a bit more too as the PE is too evident as well.

East guiding at 30 deg Dec

South guiding at 60 deg Dec

I've checked all the guide scope mounting bolts and got a fraction of a turn using the actual hex wrench compared to the screwdriver I normally use. The guide camera wasn't as tight in the rotolock as it could have been but didn't seem to move. No sign of any good weather for the next week so unable to do any more checks. 

Alan

As an update to my 2021 post, the camera offset is now accessible and changeable via Ascom. Not that changing offset with gain is worth doing nowadays, though it was fashionable when CMOS cameras first came out.. 😏 

Alan

@Jeffrey Johnson Here you go Jeff. Here's a list of what's included in order of date. Mixture of native and Ascom drivers including those from when the filter wheel driver was separate. My old PC just had one from 2016. Hope you find one that works for you. 🙂

Old_Zwo_Drivers.zip

Alan

1 hour ago, ollypenrice said:

Your wish is my command! 

Thanks Olly. 😊

Alan

That's nicely animated Olly,  and gives a good indication of what they're looking at for the less seasoned observer. 🙂

Alan

1 hour ago, Jeffrey Johnson said:

I know the thread here is a bit old, but if those older drivers are still available by "symmetal" I would be super appreciative!

Hi Jeff,

I just checked and they are still on my hard drive. 🙂  I'll bundle them all into a zip file and upload them either here or MediaFire cloud storage tomorrow. I may have even older ones on my old desktop PC so I'll check there as well.

Alan

1 hour ago, DaveS said:

At least you got rid of the reflections quicky. I didn't from my ODK 12 and assumed that the poor calibration was my fault (A bad workman etc). Turned out (Thanks to Oddsocks for the tip off) to be reflections from the tapered M82 - M68 adaptor. Cured by painting with Black 3.0. I only lost just over 2 years worth of images   

That's a real pain that you had it for two years Dave, before finding a fix. There are a couple of topics on CN concerning issues with the Baader UFC system on the RASA 11 causing rainbow flare effects (with a colour camera of course) on many images, with masking and flocking tried with varying amounts of success. I thought the 3D printed shaped tube was easier to try. I was going to get Black 3.0 but the UK was out of stock and Semple's ebay site seemed the only source, with no indication that they shipped to Europe, so I thought I'd try Musou Black which was available next day from Amazon, though more expensive. They seem very similar in their blackness.

How robust is the Black 3.0 to abrasion? Not that that really matters inside the scope, but would be handy to know for the future. I did use a brush for the first try but the finish was not so great at shallow reflection angles. Musou do recommend spraying it in many thin coats, and that did produce a much better, uniform finish.

Alan

2 hours ago, gorann said:

That is a relief. I doubt the EQ8 would wobble this much so could it be that the guide scope is moving?

Hopefully it's something as simple as that. I'll give it a thorough check over when it stops raining. As the trailing direction changes by 90 degrees between East and South it must be gravity related.

Alan

15 minutes ago, gorann said:

Yes, with my SCTs and refractors I use OAG and I always use that when possible (so not on my RASAs). Do you have version 1 or 2 of the RASA11? I remember reading that version 1 had terrible problems with mirror movements which prompted version 2.

Mine's the version 2. The version 1 has three visible mirror locks mounted on the rear panel. They're blanked off on mine. I've rechecked focus after doing flips and there is no change in focus or any noticeable change in tilt effects, (apparently very evident on the v1), which makes me think the mirror is stable enough not to move during an exposure.

Alan

37 minutes ago, gorann said:

For NB imaging I use 5 min exposures and see no reason for longer ones. Strange that you are getting trailing with such a short focal length which is usually forgiving. I got my dual RASA8 rig on a Mesu 200 so a different beast than the EQ8, but then I have a 40 kg 14" SCT with 3.5 m focal length on an EQ8 in a second obsy and that one does not show trailing. Something is wrong somewhere in your rig.

Thanks Göran, Do you have an OAG on your SCT rig as they are usually preferred with a SCT I can only think it's mirror movement in my case, or it would show on the guiding. But the mirror moving would generally give two distinct stars side by side, while this seems like a continuous movement only occuring after 5 mins which is odd. The shift from 5 to 10 mins is much more than any shift from 0 to 5 mins. 🤔

47 minutes ago, Elp said:

Check the musou, I've read it works at stopping reflections due to it being uneven and textured, so it's quite flaky. I wouldn't want it anywhere near any optical surfaces if this is the case.

The manufacturer does say that the paint has a low surface strength and any surface abrasion may cause it to detatch. As nothing rubs it when in place and it doesn't touch the glass I hope it will be OK. Rubbing a test piece with the finger surface seems OK, though using your nail will scratch bits off and what's left will not appear so black.

Alan

Having fitted the Baader UFC tilter unit to the UFC filter assembly I've got the tilt corrected pretty well for the full frame ASI6200. The UFC system was causing terrible flares from modest brightness stars significantly outside the FOV as shown on my previous post with the ASI2600MC. This is a common problem with the RASA 11 and UFC system.

I seem to have fixed this by 3D printing a funnel/barrel shaped piece  to fit from the rear lens element and down inside the UFC assembly to the filter. I was going to fit flocking to the inside but the funnel portion made cutting pieces a bit awkward so i thought of trying 'super' black paint and bought 100ml of Musou Black which is rather expensive.  I sprayed it over the end and inside with a cheap airbrush kit and it looked good. It seems to have solved the flaring too, even on full frame which is a relief. Here it is next to un unpainted one. Even at shallow angles with a bright light there is little reflection visible.

Here's a test 30s Lum exposure with a quick arcsinh stretch showing pretty good stars over full frame and not much vignetting either. Very pleased. 😊

Now for some NB OIII as a long exposure test. The Flying Bat was at 30 degrees in the Eastand rising. so tried a 10min exposure. Oh no. Horrible stars. Polar alignment is pretty much spot on with the odd small dec guiding adjustment required every 1 or 2 mins. The guiding trace was no different in excursions for the 10 min compared to a 1 min exposure. Oddly top right shows trailing in a different direction. Guide scope is well aligned with the main scope.

5 subsequent 10 min exposures were just the same. The weights were vertical, so I tried a target in the South where they were horizontal and East heavy and got this after 10 mins.

The long image axis is parallel to RA all the time. Guiding in all cases showed no large excursions which would cause this.

I found exposures up to 5 mins showed no trailing, while those over 5 mins did to increasing amounts depending on their duration.

It can only be differential flexure, but it's very consistant, while I would have thought flexure or mirror movement would be rather random in its effects. Anyone have any ideas?

Here's the scope on the mount. Note the 3D printed rings to allow the scope to lie firmly on its side when attaching to the mount via the adjustable table. They also give a good plug fixing points for the flocking lined dew shield I also 3D printed.

I hope I'm not limited to 5 min exposures maximum with this setup which kind of defeats the money spent on the fast NB filters. What's your longest exposure with your NBZ filter @gorann?

Long exposure imaging East causes trailing in Dec while to the South causes trailing in RA should be a clue, but if the guiding shows no problems it can't just be a balance/backlash issue as that would show continuous corrections in one direction  which doesn't happen.

Alan

Most spectacular Olly and Co. 😊

With regard to the brown dust which stands out well, do you know what's causing the blue coloured 'dust' to the right of M42. There don't seem to be bright blue stars nearby, and if it was OIII emission I would have thought it would be a bit greener.

Also, it might be worth producing a version where Orion's main stars aren't so muted, so the image is more recognizable to those who just know Orion from the naked eye view. 🙂

Alan