jimjam11

Are you focusing manually or electronically? I have noticed that focusing by b mask gets me to rough focus with my equipment (say 4" fwhm) but if I focus via the hfr measurement in sgp I can get much lower (as low as 2.5" fwhm last night) with a ha filter. Ha is definitely lower than broadband but the focus exposure needs to be long enough to get enough stars for sampling. (I measured my fwhm on 5m subs in pixinsight using Moffat 4 within subframe selector).

I would have thought so as well. When I had my AVX and was imaging at 1" pp my guiding would routinely be around and sometimes over. The result for me was bigger stars, not elongated if the guide error was approximately equal across the axes. I assume your guiding is therefore struggling on one axis more than the other?

A couple of nights ago I left everything running overnight and it appeared to behave flawlessly in terms of guiding etc, but I notice eccentricity became progressively worse. It started at approx 0.5 (not brilliant) and ended up > 0.9 (totally unusable). The direction of drift was always identical and looks like a combination of RA and Dec (RA axis is almost vertical in the screenshot). Guiding was consistent all night at around 0.6". Image scale was 4" pp so I assume this was flexure?

I have the Nevada bench supply that I want to locate in my shed, but this would mean a run of approx 15m to the mount. Measured amps is typically 3A but peaks at around 5 if slewing and running the initial camera cooldown. I have a 5m cable like this which works perfectly but I need to get another 10m away: https://www.firstlightoptics.com/astronomy-cables-leads-accessories/lynx-astro-silicone-power-cable-extension.html Should I buy another couple of these or is there a better way? Tia,

The 1.25 filters are easier to install in the filter wheel but they are not recommended below f5. 31mm filters are noj standard and slightly fiddly to install but they are rated to f2. 36mm is another standard size so I guess it would be usable in other filter wheels/systems...

This isnt really a DIY question but i didnt know where else to post it: I am lazy and wanted a dome, but this was deemed unsuitable by the garden planning officer (wife). I have been told a wooden structure that looks like a summerhouse would be acceptable but I dont feel like a big DIY project. My needs are fairly simple: Permanent structure big enough for cem60 with 200p and ed72 mounted. Imaging only, dont need a warm room etc. I think 8x8 would be a sensible size? Fully automated roof which can be integrated with a cloud/weather sensor and controlled by laptop/sgpro etc. I don't really want to build anything, I would rather buy and have it installed by someone competent. Any suggestions who to ask, what I should be looking at, what companies offer this etc? Tia,

Before I bought a polemaster I used the red light on my head torch. It was easy to hold in the right position for the time it takes, and it was one less thing to lose...

Learn your optimum lens settings before you go, that eliminates a significant variable: https://www.lonelyspeck.com/a-practical-guide-to-lens-aberrations-and-the-lonely-speck-aberration-test/ Might be some optimal camera settings info here: https://www.lonelyspeck.com/sony-a7iii-astrophotography-review/ http://www.photonstophotos.net/Charts/RN_ADU.htm At the focal lengths you mention, anything like the star adventurer will track accurately enough to be sky limited even in dark skies. The included polar alignment scope will get you close enough with ease...

About to embark on a similar project with a pulsar dome which leads me onto a very simple question: How did you route power and weather monitor cabling into the dome? As an aside have you looked into any of the smart home products as a way of automating certain aspects (power, light etc)?

That is quite a sight! Once you get it properly collimated it would be really interesting to compare your FWHM's before and after. The difference should be substantial!

Downloaded it today, very impressed so far and performance with the native asi driver seems excellent, way better than sgp.

Yes, but even with a download time of 1-2s SGP then slows everything down. It is highly synchronous in its architecture and when I tested 1-2s of download became an interframe delay of 12s+ if image history (super useful) and filter interleaving was used. SGP also has a bug whereby it 'settles' between every frame which needs to be set to allow for dithering.

How is the performance? I love sgp but it's performance is terrible with cmos cameras where exposures are short (<30s). Sgp with the interframe performance of sharpcap would be the bees knees...

An update: I am still not convinced the mirror isn't adding a small amount of blur but I havent had the weather to test this very well. However, I tweaked my collimation again and when manually focussed I was getting FWHM measurements as low as 2.4" (so 2.1px) which suggests the mirror is ok? I got beginners luck with autofocus in SGPro and it worked from the first time. However, after tweaking my collimation it would never get back to good focus after it ran the routine. I eventually realised I had manually racked the focuser when recollimating and the skywatcher motor had slipped on the shaft introducing conserable play. This is now fixed so I need some decent sky to see if I can consistently get in the 2-3" FWHM range...

Likewise, it just works and easily tracks <0.5" if the sky allows. I love running the phd guiding assistant and it telling me there is no backlash to compensate for! The magnetic clutches are different to other mounts and need to be learned but they make balancing far more precise and it clearly works...

So your image scale is the same as mine (newer version of ota, same camera, same cc) but your fwhm is approx 1-2px lower. Interesting.

I revisted some of my better FWHM subs and noticed the Subframe Selector tool was identifying a lot of stars (3000+) vs 300-400 for my ASI1600 subs. By tweaking the Star Detection parameters (mainly the hot pixel filter) my stars detected reduced to 400ish and my FWHM rose to 4.02"! I checked/tweaked my collimation, it was already ok. The weather has been poor but I managed a handful of 30s test exposures around M81 and my average FWHM was 4.3". I am going to try some tests with my ST80 and HA filter on the ASI1600 to see how my FWHM's compare. If the seeing is really this bad then I would be better with something like the 8" or 11" RASA... I would still be interested to hear what others are getting in terms of their normal/best FWHM and what equipment they are getting it with.

Similar plots for the best and worst 5min HA subs:

Eccentricity in the image is 0.438 according to Subframe selector so that seems pretty round to me? Agree that the field doesnt look perfectly flat, but it still feels like the best FWHM is too big (support images from FWHMEccentricity in pixels below)...

https://www.cloudynights.com/topic/594258-whats-your-best-fwhm-imaging-challenge-optimize-your-resolution/ I read through this topic on CN and some of the results are amazing, but it motivated me to look at my image FWHM and see what they are like. Looking back through my data for the last few years and running it through the latest PI Subframe Selector: 2015 - 4.86" 2016 - 6.5" 2017 - 4.15" (Only 2 nights of data found) 2018 - 5.5" (Only 2 nights of data found) 2019 - 6" The data I looked at ranges through a 500D, 100D, 80D and ASI1600MM Pro (2019 data), but always with a 150p with coma corrector @ 680mm. My best ever FWHM was in 2016 at an amazing 2.18". However, it is clear my average is 5+ based on the majority of the data. 1. Does this confirm my seeing is pretty horrible (Central Scotland) which means I am oversampling considerably (ASI1600 @ 680mm = 1.15" pp)? 2. It could be collimation but I check regularly and it doesn't seem to drift much. 3. Not sure if my mirror coating is breaking down which is leading to elevated FWHM: This is not dust, dirt or anything easily removable; I have cleaned it a few times believing it was just dirt. The picture does make it look much worse though! My most recent (unfinished) image can be seen here and the stars look good, but the FWHM is allegedly 5.24" which seems really high! https://www.astrobin.com/390632/?nc=user 4. Something wrong with the measurement in PI? 5. Poor tracking leading to inflated FWHM? This is definitely a possibility but my latest image had a guide RMS of 0.8" with both axes < 0.5". 6. Poor focus, since getting the ASI1600 I have been autofocussing, my SGPro HFR seem pretty consistent and they dont inflate substantially when going from an 8s focus exposure to a 5min sub. I think this supports the idea that tracking isnt the issue (at least not in all cases). 7. Something else?

Now that this mount has been out a while what is the consensus on its guided performance, and ease with which it delivers that performance in the lovely British weather? Currently have an avx but like many people thinking this or the cem60 could be a great step up. I want something which is reliably seeing limited so I can stop fighting with my overloaded avx (which is great with less weight), and actually make the most of our limited clear sky...