iantaylor2uk

I fitted an electronic focusser to my TAK 102 TSA (it was pretty simple, and the standard ZWO EAF fittings worked, provided you use a 5 to 8 mm coupler - I ordered one quite cheaply from amazon - the one I used was: https://www.amazon.co.uk/gp/product/B095NBQR3P/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1) and was out last night (12th Jan) to use it with my ASI Air Pro and ZWO 071 cooled camera (autoguiding was using an 120 MM mono camera on a 50 mm guidescope). I used a 1x Hotech flattener, and an L-enhance filter. I needed dew control strips on both the main scope and the guidescope as there was a lot of moisture in the air. I have found the CooWoo 5V USB dew strips work pretty well for this set-up (again you can order these from amazon). I first tried a quick M42 - gain on camera was set to 200, sensor was cooled to -5C, and I just took twenty 30 second exposures (this would be equivalent to around 10 secs if I'd just used a UV/IR filter). Some good detail was brought out using the L-enhance filter, but the short exposures also enabled me to pick out the trapezium quite well. Next time out I'll have to take an hour of these + some longer exposures (say 2 mins) and combine the two images. Then I moved on to the Alnitak region - here I used 3 min exposures (same settings as above) and took twenty images. Finally I moved up to M1 and took 60 two minute exposures. The L-enhance filter bought out some detail in M1, but I really need to spend a few more hours on this. Results after stacking and processing are below - my guiding wasn't great - not sure if this was the seeing or because the telescope was too well balanced (the Losmandy G11 likes a slight inbalance in RA if the load on the mount is low).

My guiding was also worse than usual at an average of 1-1.3" RMS, but as I was using a WO 81 refractor with a ZWO 071 camera, each pixel was around 2", so it was still good enough. Managed to get my first good image of the Rosette Nebula (I used an L-enhance filter) - image below is from a stack of 54 two minute exposures (with camera gain at 200, sensor cooled to -5C) and then some further image processing was done in Nebulosity 4.

I would use the L-enhance filter - below is an image I took last week with a ZWO 071 cooled camera using the L-enhance filter on my WO 81 GT IV (gain = 200, sensor cooled to -5C, 120 sec exposures, offset was default value used by ASI Air Pro) - stack of around 40 images with further processing in Nebulosity 4.

You'll have more light gathering capacity with the Esprit, due to its bigger aperture. Also 120 secs sounds way too long for Orion. I usually only do 30 secs and even that usually blows the core out.

There's some discussion of flatteners that work for these telescopes at: https://www.cloudynights.com/topic/560592-rc-field-flattener/ It seems as if you may need one for the RC6 with an APS-C sized camera sensor (which was a surprise to me as I thought one of the selling points of these scopes was that they were "coma free, chromatic aberration free and spherical aberration free optics" - according to the advertising blurb)

You can adjust the tilt on the 071 MC Pro camera if you need to.

I think it would be much easier to do this in python

Here is one from me. Photo taken on 5th Jan 2022 with WO 81 GT IV refractor with 1x Hotech flattener and L-enhance filter. I used a ZWO 071 MC Pro cooled camera with gain=200, sensor cooled to -5C, and 120 sec exposures. Around 40 images were stacked in DSS and further image processing was done using Nebulosity 4.

Looks good - I would have thought you could have gone to shorter exposures with the RASA - maybe do 90 x 60 secs rather than 18 x 300 secs - that may reduce the halos on the stars.

I think if you use a filter such as the L-Enhance or L-Extreme, then there is a case for using higher gain on the CMOS cameras. On my ZWO 071 MC Pro camera, I have played with gain quite a bit, and although I have used unity gain (90 on this camera) I have found better results at higher gain (such as 200). The noise is also lower at higher gain. There have been others on this forum (and Cloudy Nights) who have also used high gain values successfully on this camera. If I'm just using a UV/IR filter, the higher gain means I can go to shorter exposures, but with the L-Enhance or L-Extreme filters, you can keep the longer exposures and it should also bring out some of the fainter details. I typically use 120 sec exposures for most DSO's when using the L-Enhance filter, and this works quite well - I'll have to try it out on the Spaghetti Nebula

Hello - I'm also in Chester too (and am a member of the Chester Astronomical Society that Jeremy has pointed you towards). I have a blog at https://chesterastroblog.wordpress.com/ This forum is a great place to get advice and learn things from. Hope you enjoy it.

Managed to image the Horsehead nebula tonight - this was with a WO 81 GT IV refractor with 1x Hotech flattener and L-enhance filter using a ZWO 071 MC Pro cooled camera (with gain set to 200, sensor cooled to -5C, and 120 second exposures). Image below is processed using Nebulosity from a stack of 32 images (stacked with DSS, and included dark, flat and bias calibration frames) - the image has been cropped a bit. Does this look better than with your L-extreme filter?

Sorry - I sent the wrong link - it was supposed to be the one below: https://www.altairastro.com/altair-starwave-v3-08x-reducer-t2-thread-279-p.asp

You could try the one below - you may need to play with the spacing but it says it works for telescopes with focal ratios of f5.5 to f8, so should work with yours. This is both a flattener and a 0.8x reducer, which sounds like exactly what you want. https://www.altairastro.com/lightwave-08x-reducer-290-p.asp I personally use a Hotech 1x flattener (which says it works for telescopes with focal ratios in the range f5 to f8) and that works well on my William Optics 81 GT IV.

If anyone is interested, I wrote a short article on astrophotography, using ZWO cameras and an ASI Air Pro, for my local astronomy society (Chester) newsletter. This was really aimed at informing people of recent advances in astrophotography that have helped to automate the whole process much more (compared to the past). Some people on here may find the article of use. All the best Automating Astrophotography Ian Taylor Sept 2021.pdf

We had intermittent clouds last night in Chester, but I managed to grab about 30 two minute exposures of the California Nebula before it started raining. I used the ZWO 071 MC Pro camera (gain = 200, sensor cooled to -5C, 120 sec exposures) on a William Optics 81 GT IV refractor, with 1x Hotech flattener, and an L-Enhance filter. Really need quite a bit longer on this target, so will try again when there are less clouds!

I think the L-enhance filter is not as bad for halos. If it is clear tonight I'm planning on using a WO 81 GT IV on the horsehead nebula with an L-enhance filter (but with a 1x flattener, so the focal length will be about 480 mm) and will post the results. I use a ZWO 071 cooled camera and will likely use a gain of 200, cool the sensor to -5C and use 120 sec exposures.

You're right on the cliff edge at a gain of 100. Just to make sure you are in the low noise region of the camera operation, I would be tempted to use a gain of 150. This still has a good dynamic range and you are definitely in the low noise part of the camera operation.

A William Optics 81 mm triplet is a good choice (I have the 81 GT IV). You will still need a flattener, you can either use a dedicated WO flattener/reducer (which will give you a focal length of about 380 mm) or a general purpose flattener (I use a Hotech 1x flattener, which gives a focal length of 478 mm). This gives good round stars right out to the edge of an APS-C sized sensor, and at 478 mm focal length, the field of view is 2.8 x 1.9 degrees, with a resolution of about 2.1" per pixel, so autoguiding should be pretty straightforward. A larger refractor will usually have a longer focal length, so a smaller field of view, which can be good for some targets, like galaxies.

How about: how to use setting circles

Why do you need exposures of 1 sec? When I use a light panel on my ZWO 071 Pro camera and set auto for flats on my ASI Air Pro, it typically takes flats at 40 or 50 milliseconds with a UV/IR filter, and they look ok to me.

I tend to use an ASI Air Pro and use auto exposure time for flats, using a light panel, and typically get exposure times around 40-50 ms with my ZWO 071 MC Pro camera (and UV/IR filter). I tend to use bias frames rather than flat darks as I'm not sure you can choose those exposure times with the ASI Air Pro.

I understand vlaiv's argument that he suggests using the UV/IR for colour accuracy but surely that doesn't matter too much since we are shooting RAW files (fits files) so we can get whatever colour we want in post-processing, can't we?

I use the Starwave 50 mm guide scope (which has a focal length of 207 mm) and it has worked well for me on telescopes ranging in focal length from 380 mm (WO 81 GT IV with 0.8x reducer) up to 1200 mm (f/4 12" Newtonian). I use the ZWO 120 mini mono camera as the guide camera. I have guided using PHD2 as a stand-alone program, or more recently using PHD2 through the ASI Air Pro. I don't like the helical focuser, and since I don't have a permanent set-up, usually end up having to focus it each time I use it.

Just swap over the guide camera to be the main camera temporarily and then you can get the value u need.