Simon Pepper

4 hours ago, Iem1 said:

Second night completed, and I discovered a method that really improved my guiding I think...turning the guiding on.

After figuring that out, there was no 10-20 seconds of accuracy before the upwards spiral.

as an average I would say i was achieving;

RA ~ 0.75"

Dec ~ 0.35" 

My PA

Guiding

3 minute sub of the Cygnus Wall 

Are these values within the realms of what is to be expected for my set up? ( RA ~0.75 & Dec ~ 0.35)

Also, I think I might need to adjust my dithering intervals. It was set to a 60 second 'wait' during the dither, but the figures for guiding did not show as settled (back to the average 0.75 etc) until well into the next 3 minute exposure. I'm not sure how "live" the feedback is, but if it's pretty spot on then half my exposure time has been with high values for RA Dec due to the disturbance caused by dithering.

I will post one of the actual subs from my laptop in the morning for closer inspection.

Any tips/feedback are most welcome as always, cheers guys. Appreciate the guidance (pun intended).

Now that’s a PA! Also my best guiding ever that I saw anyway was 0.56 so you one up already! Glad your sorted it!

If you have issues again tonight bosh it here I’ll be out trying to figure out my mosaic that fantastically failed last night as well

You need a good PA guiding and PA are separate anything with a smiley face will be good in the AAP but this does depend on focal length. There is another setting something about restoring from last session make sure that’s off as well and make sure when calibrating that the steps count up to at least 12 West and back and 12 north and back. 

29 minutes ago, ollypenrice said:

This rings alarm bells for me straight away: 'I focused and PA well via the ASI.'  Does this mean you believe in your PA because some software tells you its good?  I've had plenty of experience of software not being accurate in this regard. Once aligned I would do a simple drift test like this: point the scope towards the celestial equator in the south. Set up a 3 minute sub and, during this exposure, track at the slowest possible speed for 1.5 minutes one way in RA and then 1.5 minutes back again. This will produce an outward star trail and a return trail. If the PA is good the star trails will overlap, producing one single line. If PA is out you'll get a shallow angled vee. This test is software-free and direct so it can be believed in implicitly.

Being suspicious of all things software I also prefer to guide by the simplest means possible and that's by the old fashioned ST4 cable. This means no 3rd party software, just the camera, the mount and PHD involved.

Olly

I think you are right to suspect as I can one day the PA accuracy on AAP is not perfect but it’s good enough. Also AAP runs PHD I thought so there is no additional software here other than ZWOs OS? ST4 is dated now the OP has everything correct with cables I think the issue is RA only is on in AAP. Thanks 

Hi Lem

i have - similar setup. What guide scope are you using? That focus is fine by the way. I see you have a star tracker too and I can’t see the RA line have you left the guide the RA only box on? Couple other things. Clear calibration every time depending on guide scope you may need to lower the steps let me know

Thanks

James If I were Look for a wide lens can’t go wrong with Samyang 14mm for you canon you should get around 15s subs untracked with that take as many shots as you can get and stack them. You will be going after wide field Milky Way shots. Next step up will be a star tracker you can pick up both these items for about 400 quid used I reckon. 

I do all my processing in PI I was PS back in the day and still have it but for me PI is incredible. I use the WBPP script for stacking in there. Don’t quote me on this as I use a dedicated camera but pretty sure you want an canon eos clip in filter but do check with others here as I know when modified some clips may not fit others here can hopefully advise on this. Thanks 

So I have had a quick go at this, but I agree it was a struggle to pull out the Ha and Oiii. I am not sure how you got on, but here is what I managed in 20 mins. We could spend another few hours sorting out gradients, vignette etc but my kids just woken up again!!!  I cant see the  Eastern Veil here so I think the light cone at the bottom is probably the back end of it hence the blueish light near the bottom. So a few ideas I have to improve the data is definitely take calibration frames especially flats they are your friend will sort the vignette and any dust moats and will allow better stretching. Also putting in an lenhance or lextreme or any dual NB filter clip in for EOS will be a game changer for you. Your tracking is good and so are your stars (note I killed them here with a bad mask and too much sharpening)! Flats and dual pass filter and you will be loving it!

I will have a look at this later as the kids are driving me insane this will be a nice escape! However can’t guarantee anything as calibration frames are a must especially on an uncooled dslr in this weather 😬

36 minutes ago, alacant said:

Hi

Flex. This is when the guide telescope is moving relative to the 127 as the assembly changes angle. This is because you have it mounted on the flimsy finder shoe.

Instead, put the asair in the finder shoe and mount the guide telescope properly to the handle.

Here is an example of how rigid the assembly needs to be. This rigidity is needed even over just 420mm focal length. At 1 metre, it becomes even more imperative.

The OAG will of course do it, but represents more expense and more work to have to do. 

Cheers and HTH

 

Thanks for this the OAG just turned up so will try this fingers crossed! 

3 hours ago, newbie alert said:

Looks like in 1 direction.. could be backlash, pa, balance... What's the light area  circles at the top of the image?

The bottom of M51  sorry zoomed in there. Thanks 

Hi all 

Firstly apologies for bringing this up again but I decided to run some tests last night with the clear hour I had. I also stripped down the OTA, replaced extension tubes and changed the compression rings on the flattener closer to the compression ring on the ES to ensure good connection. I am 99% confident there is no sag in the focuser or anywhere along the OTA. Guiding was awful between 1.1-2.2.

• There is not much change in the way of elongated smaller stars between 20s and 180s (60s vs 180s below). As my guiding was bad I would have expected to see even worse stars at 3 minutes but they are not too bad even at 5 minutes. Yes they do get worse but I expected more.
• Pretty sure even after 1s/2s they were trailing but hard to see due to lack of exposure. Its like the issue happens as soon as the exposure starts. Correct me if I am wrong but if PA is aced at 950mm should I be able to get 5/10 s before trailing? 
• I turned off guiding and things got worse after 30s (expected really).
• I tested on M13 and M51 both quite near the zenith. 
• I do have backlash I can wobble both axis so could be this also.

I believe this has to be either flexure (which I don't really know what that is) or the fact my guiding scope is only 120mm. Unfortunately I don't have the correct attachments to try the Redcat as the guide scope, however I have an OAG on the way to try that out. This option was a lot cheaper than the EQR6! I will report back my findings once it arrives.

Thanks

On 08/07/2022 at 16:42, newbie alert said:

Before you have to dig deep, or drive yourself into a state of frustration , your  big stars look roundish and the small stars much more oblong... I've had this with a William optics and it was focuser sag... So worth checking that everything is tightened down 

Well funny you should mention this because I wondered how the bigger stars were unaffected but I heard somewhere that could have something to do with pixel scale... I assume I can test this by pointing up to the 
Zenith and taking a long sub? Also did you just tighten them up? Mine is tight but it’s the standard hex focuser. I feel this could now be three or four potential issues and no idea how to narrow that down 😭

I feel I am going to have to dig deep into the wallet again then and speak to FLO who have four in stock! 
 

Thanks all for your help with this one really appreciated. 

18 minutes ago, AstroMuni said:

I looked up the ES127 here https://www.rothervalleyoptics.co.uk/explore-scientific-ed-apo-127mm-f75-aluminium-essential-triplet-refractor-ota.html
And if we are talking about same scope, I think you could be stretching the weight limits of the HEQ5 Pro.

I think there weight is wrong there or its the shipping weight I got mine here https://www.bresseruk.com/EXPLORE-SCIENTIFIC-ED-APO-127mm-f-7-5-FCD-100-Alu-HEX.html?mtm_campaign=Doofinder&mtm_kwd=0112134&mtm_source=English&mtm_medium=OnSite&mtm_cid=UK&mtm_group=SiteSearch which states its 7.7kg with accessories. Mine probably a little more with updated dove tail, filter wheel camera etc but pretty sure I am only about 8.5kg so well under the max weight. 

8 minutes ago, Clarkey said:

Keep her away from your scope🤣

Looking at the image I would say there are two things that will improve your guiding.

Firstly a bigger and better mounted guidescope to ensure no flex. Secondly adjust the mount to get the RMS down.

Haha amazing! 

24 minutes ago, AstroMuni said:

Could this be due to balance? Otherwise cant see why a different scope can change the behavior of the mount.

I can get slightly better with my wife filed scope as it’s lighter not so demanding I think. Also at 250mm I can expose for longer without any trails. 

3 minutes ago, Elp said:

If you've still got the widefield scope you could try mounting that as your guidescope as a test.

Proper Dec and RA balance is the easiest thing to check first.

Ooo another awesome shout here is a pic of the setup. Balance and PA are good at least I thought they were lol. 

2 hours ago, Clarkey said:

With regards to the star shapes this does look like a guiding issue. The RMS you are getting is not very good for an HEQ5 - it should be well under 1. The Rowan upgrade will help, specifically if there is significant backlash, but I do find my HEQ5 does require regular 'tweeking' of the worm drive to keep the guiding to its optimal. The end float on the bearings is also critical. I think you need to get this better before going to OAG as you may end up with the same problem.

As for the black mark - this definitely looks like dust/dirt close to the sensor - probably on the sensor glass.

Thanks this is really helpful I guess it’s time to try the belt and maybe a full strip down and re grease! 

1 hour ago, AstroMuni said:

Have you tried to see the longest duration you can get without guiding? I can easily get 30s with no elongation and mine has no Rowan modification. HTH

I can get 15 minutes subs on my other scope but as soon as a put this scope on it goes toilet on me. I tried 30 seconds and there was. I difference between that and 60s. It’s almost instant… 

3 hours ago, Elp said:

Does the guidescope pixel image scale match the main scope? I don't read too much into the technical side of things but I found when I changed from a 30/120mm guidescope to a 50/202mm my guiding improved by approx 0.2rms at least when the seeing was similar. The improvement was better when using an OAG but I went back to the guidescope. For a long refractor are you positive the balance is spot on.

You could be into something here I wonder if the difference in FL mm could be causing it. Guide scope is 120mm and main scope is 952mm it maybe too much of a gap! 

Hi all

I need expertise again I am consistently struggling with this scope and I am considering just selling it! Probably had it a year now and not managed one respectable image! Its so annoying as when it comes to widefield I have no issues. I get that this would be harder but really a year....

I assume my elongated stars are a guiding issue they do all appear to be the same was but these are only 60s subs surely that should be obtainable? I see others with similar setups on the same mount not having this issue. I am thinking about getting the rowan upgrade for the HEQ5 and going down the OAG route but before this costs me another £500 I want to be sure this is the issue?

Flats as well with this OTA are doing my head in I cant remove the black mark and I also have no idea where this is coming from. Its not the filters as its on more than one, its not the camera sensor as I shoot on my widefield scope and don't see it, so that leaves the scope, but I don't see any issues on the OTA and I cleaned the lens yesterday so its not that! Why wont the calibration remove it ahhhhhhh!!!

I have screen shot lower right corner of the image you can see the corresponding dark spot from the master flat. I have attached the masters as well. Also the trailing is more evident on the fainter stars I think my total RMS was 1.2-1.6 I guess this is just not good enough?!?!?

masterFlat_BIN-1_FILTER-R_Mono.xisfmasterLight_BIN-1_EXPOSURE-60.00s_FILTER-R_Mono.xisf

Vlaiv tried to assist here: https://stargazerslounge.com/topic/396743-flats-issue-with-larger-scope/#comment-4260660 but turns out the compression ring was not causing any of these issues.

Thanks

Well this could be something to do with it.... I am not sure if this came off as I took off the flattener (I don't think so) or if its been sitting in the OTA like this for months if the latter this is very embarrassing. Its a compression ring off the end of the hotech flattener. I have removed the extension tubes and compression rings and have noted a small metal chip on one of the threads of one of the extension tubes its silver so could be reflecting? Also there are 3 small screw ends entering the tube one from the focuser I think and then two further back not sure what they are or whether could be causing any issues I doubt it though I believe they are normal.  

20 hours ago, vlaiv said:

My bet is on this one.

There is calculator that can tell you approximate distance between dust particle and sensor depending on F/ratio of scope, pixel size and diameter of shadow. Do search net for one of those to help you diagnose possible location of dust particle.

As far as calibrating it out - it should calibrate out if you use proper calibration.

Any "shortcut" can cause under / over correction (like using bias instead of proper darks or skipping some calibration files).

Looking at image that you posed - Blue filter seems to have over correction on vignetting as well that is visible (there seems to be circle in background of different intensity?).

What is your calibration workflow?

Nope.

In order to get proper color in stars - you really need to do full color calibration.

To the first approximation - you can scale R, G and B channels based on photometric measurement of a star of known temperature, but in reality you want to use color correction matrix rather than simple weights.

If you don't want to mess with all of that (and it is a bit more technical) - look into Siril for example, or given that you have PI - there is also "photometric" calibration tool.

These are of questionable quality, but many people use them and will therefore produce "expected" looking image (although often not really correct).

Hi Vlaiv thanks for taking the time here and apologies been a hectic day! I managed to get M13 looking ok colour wise I did the photometric colour calibration in PI and made it a lot bluer, but definitely a lot better just played with curves etc and I think its about right now. So as for the flats my procedure is to use a flat panel with the bigger scope as I don't have a big enough t shirt also I am lazy and take them the next day but I don't move the OTA so pretty sure I can get away with this (no issues with other scope doing this). These particular flats were only 30-60 milliseconds, but the ADU value was around 30,000. I will remove the flattener to see if I can see anything obvious on that that could be causing it. Do you think its a dust moat or something else? 

Thanks