cfinn

Thanks for your reply. And yes, that cable was a bit taught on this occasion. It could have had a bit more slack in it but pretty sure it's not an issue as it's plugged into the Pegasus PPBA on top of the scope. I've had the mount since September and it had a bit of play in RA from new. Like you I dialled it out using the Astrobaby guide to the point where I can barely feel any backlash. Slewing the mount 360 degrees in both directions revealed no binding in the gears after that procedure so I stopped there. I could return to this and adjust some more but I am not sure there is much adjustment left in there before I get binding.

Hi all, I'm having a few issues with guiding my EQ6R-Pro. Specifically, I am finding that guiding error in RA is 2-3 worse than in DEC and my overall guiding RMS is quite a bit larger than 1 arc-second. The results are varied through a guiding session, with stable periods and periods of large (2-3 arc-second peak-to-peak) oscillations in RA. I would expect to be regularly achieving < 1 arc-second guiding RMS with this mount based on other user reports and manufacturer's spec. It's worth noting however that this problem is virtually non-existent when I am guiding closer to the pole, e.g. around Ursa Major, where I can achieve results as good as 0.5 arc second RMS quite easily and am consistently well below 1 arc-second. The problem emerges when I guide well away from the celestial pole. I talked through my issues with a few people on the StarGaZine Zoom call last night and am sharing here the full details and guide logs to source some more help in getting to the bottom of this problem. A few details. On the mount I have an Esprit 120 and I am guiding with an Evoguide 50 and a ZWO ASI 120mm mini. I am attaching a photo of my setup and am fairly convinced I am following all the best practices with cable management, at least as far as is possible with this mount. Moving the scope into all feasible positions I experience no obvious cable snags. It's quite a heavy setup, getting on for 14kg I think, but this mount should be able to handle that. I have tried perfect balance (both axes) and balancing East heavy in RA and found very little difference in the results between them. In terms of guiding software, I am using KStars/Ekos and the built in guider. I have tried PhD2 as well and experience very similar results. I am using multi-star guiding with the Predictive PEC guiding algorithm with guiding exposure set to 1s, min-move set to 0.1 arc-seconds and aggressiveness parameters fairly middle of the road so I am correcting around half of the measured deviation. I am including a screenshot of my typical settings below. I have tried longer exposure times (up to 3s), and lower/higher aggressiveness parameters to no avail, so I am fairly convinced that my problems are not due to "chasing the seeing" or bad configuration, particularly since I see good results closer to the pole and bad results away from the pole on the same night with the same settings. In all configurations, if I am pointing more towards the celestial equator I see the same pattern of large RA oscillations that come and go in an apparently random way. You can see this in a screenshot I am providing from PhD2 log viewer. I am attaching two guide logs to help diagnose the problem. One is from a session on 23rd January, when I was imaging M81 and M82 (you can see the result here). Guiding on this session was good, and what I would expect from this mount. In this general area of the sky closer to the celestial pole, I am not experiencing any problems. The other log file is from last night, where I was imaging the Pleiades and it is quite erratic. This is quite typical when I am imaging closer to the celestial equator. You can ignore regular spikes in RA and Dec as this is where I was dithering. Lastly, it was suggested to me on the Zoom call last night that I should take a look at the RA belt drive and see if there were any problems there. I am including a picture of this as well and there was nothing obviously wrong to me there. I don't feel any stiffness in the mount and everything moves quite freely. Certainly enough that I can deliberately balance and unbalance the mount at will. I hope all of this detail will be useful in helping me to diagnose my issue and I would be extremely grateful for any help you can all give me. Thank you, Charles guide_log-2021-01-23T20-31-58.txt guide_log-2021-02-28T19-05-28.txt

With regard to cooling temperature, I think -5C or even 0C is more than enough with this camera. I won’t be using any less than that with mine when it arrives. Dark current is completely negligible at these temperatures and will not contribute meaningfully to noise in the final image so there is no benefit to cooling below this, particularly with typical sub exposure times being < 1000s (including narrowband). Read noise and photon shot noise (light pollution) will be the dominant sources of noise here. The only reason I can think of to cool below -5C is if you experience extremely cold winter nights, which I appreciate some might.

Quite pleased with this for only an hour. Completely processed in APP. SW Esprit 120ED, Nikon D5300 (unmodified), 30 x 120s I have a QHY268M on order, which is exciting, but I am still really impressed with what can be achieved by the Nikon. Bang for buck it is incredible and I would highly recommend it.

The images on your website are really fantastic though, congratulations. I would say it's worth it

And here's a bonus starless version of the above created with starnet! I used the spot healing tool in Photoshop to clean up some star removal artefacts and used the original image as a layer to blend back in Gamma Cass, whose intense UV emission is responsible for the blue light reflecting off the dust and for the red glow from the nebula through hydrogen recombination seen here in Ha.

Here is my entry. Channels combined in AstroPixelProcessor using SHO scheme using Ha as a luminance layer and with the following RGB weightings: SII: R=100, G=0, B=0 Ha: R=80, G=100, B=20 OIII: R=0, G=100, B=100 I then followed this up in Photoshop with levels adjustment and selective colour to reduce magenta and boost blacks slightly. This recovers more natural looking star colours and darkens the background a touch. Lastly I boosted the blue mid tones slightly to get to an overall colour balance I was happy with.

Indeed, since you said that I have taken a look at my individual subs and they show the same thing even at the end of a several hour session. Like you though, I'm not overly concerned about it and it does seem to be extremely common to varying degrees if you look at images on astrobin.

Really impressive for only an hour of integration time. On the topic of pinched optics, my Esprit 120 shows brighter stars being slightly hexagonal but I very much suspect a lot of this is due to there not being sufficient time for the scope to acclimatise from warm room to cold outdoor temperatures. This could well take a couple of hours when it’s really cold outside. If you’re setting up from scratch every night as I am, this could be a contributing factor?

Thanks for the advice. I definitely don’t want to push it too much given the integration time. Hopefully I can add some more data later in the spring. Fingers crossed we have some more luck with the weather soon!

Thanks all! 🙂

Many thanks! I might take it into Gimp or Photoshop to see what I can do with the colours.

I setup and tear down my Esprit 120 on an EQ6R-Pro every night I go out, both for imaging and visual and it is just fine, though I certainly wouldn’t want anything heavier. It is absolutely rock solid in every respect and everything works very well indeed. I think the Tak TSA-120 looks particularly svelte and will be lighter and easier to handle but on the downside it comes with a big price premium. Optically I suspect it will be very difficult to tell these two scopes apart, though common wisdom dictates the Tak will have the edge.

This is 2.5 hours (50 x 180s subs) with my SW Esprit 120ED and unmodified Nikon D5300 under a 77% illuminated moon last night! Processed using Astro Pixel Processor with 50 x flat and bias frames. I didn’t bother with darks, just dithered 10 pixels after each exposure, which was very straightforward in Ekos. All things considered, I’m quite happy with how it has turned out. I would have preferred a moonless clear night but I can’t remember the last time we had one of those! Feedback very much welcomed. Charles

Same for me as well and I've had no issues. I have seen some similar discussion about this on Cloudy Nights and it wasn't an issue for anyone commenting there.

Thanks, yes I was advised on this previously but wasn’t convinced the recommended dovetail would work with the existing one. I think I just need to take a closer look at the specs. Thanks for your help!

Yes I’ve thought about something custom as well. Shipping is already disrupted by covid let alone pending no deal Brexit! 🙄

Many thanks!

Hello @Miguel1983. Thank you for sharing all of this. I would be interested to know the exact losmandy dovetail you purchased if you wouldn’t mind sharing that info? It seems difficult to find one that will pair nicely with the existing green plate, as the length seems to be non standard. I am worried the holes wouldn’t line up with most of the options out there. Thanks!

Dwarf stars far outnumber any other kind of star in the Milky Way, but by virtue of their small size and luminosity there are few that are visible to the naked eye. However, I suspect they start to dominate in long exposure images, even with amateur equipment, hence why the majority of the fainter stars have a yellow/orange cast to them. Hotter, more luminous stars (white/blue in colour) are relatively rare by comparison, but they dominate the naked eye view alongside red giants.

Thanks for the responses! The double cluster was something I was thinking of. Bright and far enough away from the moon I think. I’m working with fairly new gear as well, so it’s definitely an opportunity to test things out. It’s funny how localised the weather can be isn’t it? I’m in the South East corner of Kent and it’s been clear blue sky since 9am! Charles

Hi everyone! This is what I have tonight in Bortle 5 Kent. Perfect except for a (nearly) full moon! I’m imaging at f/7, 840mm focal length with a DSLR. Alas, no mono CCD/CMOS with narrowband filters just yet! What would you do?

This beauty arrived in the post on a cloudless day! Who would have thought it. Star test on Vega was almost flawless. Nice even energy across the diffraction pattern both sides of focus and not a trace of false colour that I could see. Always been a dream of mine to own a decent sized refractor like this. Needless to say, I'm delighted!