edarter

Were all your sessions at the same camera rotation? Mine are at two different rotations so applying the same crop etc is something I'm not sure of doing.

Hi, Back in January I gathered quite a bit of data on the Pinwheel galaxy and processed it, all good so far. When the SN kicked off though I revisited it and have gathered another 2-3hrs of data (unfortunately at a different camera rotation but thats another story). I have two sets of integration, one with everything included (SN data as well) and one with just the SN data integrated. Both stacked in APP, no processing done. My question is what would be the best way of processing this in order to maximise the SN data? I'm concerned that just processing the data where everything is integrated will have a reduced SN as it wasn't present in every frame and would therefore be calibrated out to some extent (it is still visible though - I've done a quick STF to check). This approach would of course give another 2-3hrs of the rest of the image though which can only be a good thing. I usually separate the stars using Starnet 2 and did wonder about somehow adding the SN only star mask over the 'all included' starmask but a) not sure if thats a good idea and b) no idea how to do it! Suggestions welcome Ed

You might already know this from the YT videos etc but the dithering value you need to put in your guiding software needs to take in to account to the difference between your imaging setup and your guiding setup. I found the following calculator really useful to help me home in on the right setting for NINA. https://www.astrohowto.com/interactive-dithering-calculator/ Hth Ed

I dont think you are alone with doing that. I'm massively self critical and compare my results to those with way more experience and better kit. Very easy to get in to a spiral of frustration then. Just be mindful of it and keep in mind its just a hobby and should be fun.... otherwise why are you doing it. Ed

Excellent - thanks Martin! Ed

Looking for advice as to which value to use for my manual average PSF in BXT. Running Dynamic PSF to calculate an average, but not actually sure which of the following is the right value to plug in to BXT? Thanks Ed

Have you got the raw stack before editing? I'll have a go and see what I can get from it. Happy to let you know the PI processes used.

If it helps you make your mind up about PI, I plugged on with photoshop for ages trying to improve my processing skills, keen to avoid the cost of PI at all costs. I'm reasonably technical and can get my head round most principles but for the life of me I didn't seem to make any headway beyond 'yeah its ok' in my mind. I succumbed to trying PI and haven't found it half as difficult as I thought it would be and was very quickly getting similar results to photoshop and I think I'm now well past that point. It's been the single biggest improvement in my processing skill set and results. Of course ymmv, but given there is a months free trial it's worth a look. Ed

Quick update on this. Some progress made but still not where I would ultimately like it to be. Last night was clear here in Oxfordshire (though I couldn't see the aurora - gutted!) So I did another session on the Horsehead. I increased the settle time to 30s and recalibrated PHD2 once I had slewed to the target, figuring that calibrating at the orientation I would be imaging at would give the best result. The good news is I'm no longer getting those pesky warnings popping up after every dither. The relatively good news is that guiding was better. I was averaging 1" total error but with some going above my 1.3ish pixel scale and which would therefore need to be ditched. What I would say though is that my guiding is nowhere near as good as it used to be. Previously I would regularly get guide errors of only 0.5-0.6". Not a chance of that last night, or indeed over recent months. I'm also getting regular glitches still on both axis which PHD2 is needing to be very forceful with its corrections to keep under control. I suspect these two are related! I think I'll do a separate post asking for people to have a look at guide logs and give me their opinions. Question - if I can feel any backlash on either axis - is that too much? I definitely feel a slight 'knock' on either axis if I try to rotate the mount by hand when the clutches are nipped up. What I don't know is how much is too much and needs tweaking out. Thanks for all the advice so far! Ed

That sounds odd, I would have thought the spacing between sensor and the front face of the DSLR would be very similar for both models. Can you post an image? Has the scope been modded at all? Ed

Thanks Scotty, I will give this a go and report back.....when these clouds b*gger off!

No, that's something I don't do very often to be honest. Will give that a go. Supposed to be clear tomorrow night so fingers crossed the forecast stays like that!

yep - I polar align using the guide scope and Sharpcap and always make sure its at 'excellent' before continuing. I assumed guiding stopped as I'm sure I've seen 'resuming guiding' come up as a message after a dither. I could be wrong though! I do wish I hadn't upgraded NINA now as it was just fine before! Thanks - next time out I'll increase the settle time. Given this is in NINA, should I completely restart the sequence after each change? ie do changes not take effect until next time you initiate a sequence. The comments about sticky axis are interesting. back in the summer I very slightly backed off the bearings in the mount as its always been a bit sticky from new. This resulted in lovely smooth rotation mostly but I still have a little stickyness rotating to the right from park on the RA. I couldn't dial this out completely without the rest of the movement being VERY free and being a bit worried that I had introduced play in to it. This has been the reasoning behind me wondering if I should bite the bullet and strip the mount, clean it all up, re-grease and sort any backlash out. Dreading the thought of doing that though in case I mess it up! Thanks Ed

ah ok, didn't realise that tube orientation was important for this. I'll another image with that in mind. Thats exactly the guide I used Took the opportunity to upgrade the secondary adjusters when I did it and move the primary up the tube a few mm so that the FT is not in the OTA much, which is now about 5mm at focus. I don't use the M42, I went straight to M48 from the get-go but it is spaced about 55mm (with a shim after some experimenting previously to get star shapes ok-ish) 60mm seems a lot further than the Baader recommendation for spacing, will that work?? Happy to try it though. Ref focusser - I've removed the rubber gromets and adjusted the tension on the teflon bush to bring the resistance back to what it was, so I would hope that this and the fact that I haven't cut the FT (and therefore its still on all the bearings) means there shouldn't be any tilt from that?! Racking in and out is certainly nice and smooth, but enough resistance that it supports the weight of the DSLR when vertical. Thanks Rick, I'll do that also Getting all sorts of issues with guiding lately which I'm also trying to fix. Treating that completely separately from this though as I suspect this one is going to be fairly easy to resolve. Dreading the thought of having to strip the mount and service it if thats what is needed for the guiding thing! Ed

So should I set the guiding settle time to zero? I didn't set it in the first place btw! I'm just concerned that this would mean that the start of every frame (I dither every frame) would then be affected by the mount/guiding settling down after the dither Tomato - thinking about it a bit more, do you see a spike in the guiding every time a dither is done? My graph 9 times out of 10 shows a massive spike in the guiding in both RA and DEC when the dither is done despite guiding being paused. This doesn't make sense to me. Ed

Hi, I seem to be going through one of those phases where almost nothing goes right and I'm hoping you good people here can give some sage advice that sees me out of this frustrating situation. Since I started guiding a couple of years ago I've never really had much of a problem, it all worked out of the box. Apart from the odd recalibration I was getting sound results of under 1 arcsec error and more often than not about 0.6-0.7. Happy days as my pixel scale is 1.4ish. However, over the last 3 months or so, on the odd occasions that the clouds have parted, my guiding has been plagued with glitches where either axis can throw a hissy fit before settling down(ish) again. I've tried everything I can think of within my knowledge of PHD2 and NINA. Balance, checking for sticktion, recalibrating, guiding assistant, even cleaning the RA and DEC clutches (which seemed to have a fair bit of grease on them somehow) but still the issues persist. one image can be 0.6 overall error and the next 3.5 or more. Last night I upgraded NINA from an admittedly old version and since then I have been getting the attached error at the start of every new frame. I have no idea how to resolve this having played with the timeouts in NINA, and the guiding is as bad as it was before. I don't know if its time to strip down the mount (NEQ6 R Pro) and service it or whether there could be some other explanation / fix? The mount has never been serviced and is probs 10 years old now. So in summary - Rubbish guiding, and now a warning in NINA with every new frame it takes. Any advice gratefully received as its really spoiling the enjoyment for me at the moment. Kit is as follows: SW 130PDS, EOS600D, Baader MPC MK3. Guiding via SW ST80 and ASI 120MM Mini all piggybacked on the 130 via a dovetail - so very solid. Software is latest NINA and PHD2 as of last night. Happy to attach guide logs if someone can point me in the direction of where they are kept. Thanks Ed

just started an imaging run and I'm getting funny shaped stars. This may not be related to the above collimation though as I've never managed to nail down the spacing of my Baader MPC mk3 perfectly. WOuld be interested to hear what people think could be causing these:

Title says it all really. I hate collimating and therefore rarely do it, which in turn means I'm not familiar with it when I do. Just spent a couple of hours doing this, on my 130pds. Does it look acceptable? Thanks Ed

ahh! that explains it lol. I can't push for an astro camera right now sadly. I am sowing seeds with my wife though about the prospect of it lol.

yes have a look at the brighter stars on the right hand side of this image...

How have you done this? I'm using a 1mm dslr adaptor and extension tube for my cc so the end of the ft is literally 1mm from the camera body, yet the ft still protrudes in to the ota by 14mm.

They are, but that doesn't necessarily mean they are optimised for it. Really, all it means is you are able to achieve focus with a camera fitted. With the most common coma correctors fitted this means the focus tube projects in to the OTA and you get Pacman shaped stars. Its a fairly common mod to cut the focus tube to prevent this but that in itself has its own drawbacks.

I've been pondering the relative merits of cutting my focus tube vs trying to move the primary up the OTA by 10-12mm. It ended up with me putting together a 'model' of the 130PDS dimensions on my workbench to see how much light loss there would be if I did move the primary. I thought others may be interested, and obviously if I've made an error here please do point it out! So what I did was mark out 650mm with 130mm marked at one end to represent the primary and a dot at the other (centred) to represent the focus point. By measuring my PDS I know that the secondary's centre point is at 435mm from the primary so I marked that point and put a post-it note there ready to draw on! Then I drew lines from each end of the 130mm marks to the focus point. Where they intercepted the 435mm line I measured and the distance between them is 43mm. All things being equal this is the diameter of the light plane from the primary at the point where it hits the secondary. I had a go at measuring the dia of my secondary but without removing it from the scope its very difficult. I got it at 48mm, and googling it after I was not far off with it actually being 47mm. So in summary, for a standard mirror position on the 130PDS: Light cone dia at the secondary = 43mm Secondary dia = 47mm Next bit was to work out by how much the light cone dia would change at the secondary if I moved the primary forward 10mm. Similar post-it modelling showed an increase in dia of 2mm so: For a 10mm forward primary mirror position on the 130PDS: Light cone dia at the secondary = 45mm Secondary dia = 47mm That still leaves a 1mm gap round the edge. Sounds enough but when you add in that the edges will be slightly rounded etc its probably right on the edge of losing light but probably ok if the secondary is centred accurately. I haven't had my secondary out of the OTA in a while, but would be interested to hear the thoughts of anyone that has as to how crisp the edge of the mirror is. I feel happier about moving my mirror forward 10mm now knowing this as I did some other 'jungle maths' which had assumed I would immediately lose light by moving the mirror forward and that equated to an 8.5% light loss. Though I'm still not 100% sure as to which route to go to get rid of my pacman stars as I actually need 14mm in total using the Baader CC!

The Baader MPC Mk3

That's really odd, the photo I attached shows the focus point with the low profile t ring used and is still 10-12mm proud, so would have been something like 23mm before. Not sure why this is? Thanks Ed