desmcm

Thanks. Good point re high clouds - there were definitely some around. More testing required……. Cheers, Des

Wretched cloud filled skies in Yorkshire prevent me from doing any sustained imaging. I did manage one 300s sub at f2 with my new asi2600mm pro (gain 100, T=-5 C) using one of the new Baader 6.5 nm Ha filters optimised for CMOS and f2. This is in fact the first image taken with the camera. Interesting to see how the Baader high speed 3.5nm version compares. Detail is good but noticeable halo on Deneb - not as evident using the IDAS NBZ and asi2600mc (see earlier post). Comparison is apples and oranges I realise but the fact that the OSC data contain OIII as well (usually more prone to haloing as far as I understand it) makes the performance of the IDAS NBZ seemingly even more impressive. Cheers, Des ps calibration, background removal and stretching of the image only.

Hope this is helpful re utility of IDAS NBZ filter with Samyang 135@f2, the following are single 180s subs, minimal processing (eg no noise reduction). I'm not very experienced in this game, hence quite excitable, but I was astonished by these single frames. Not only the contrast and detail but the lack of significant haloing on Deneb or Sadr. Camera: ASI2600MC pro, gain 100, -5C. Cheers, Des https://www.astrobin.com/users/desmc/

Hi Lee, These are fantastic images, really fab. Looks like your new Astronomik filters work a treat. I've ordered one of the new Baader CMOS optimised 6nm Ha filter for fast systems to try it out with my new 2600MM Pro. If it performs anywhere near as well as your new Astronomik fast filters, then I will be chuffed. The IDAS filter is the NBZ version not the newer UHS version. I think the difference is that the NBZ is good down (or up!?!!?) to f2 whereas the UHS is for faster systems. Happy to be corrected. I think it is a very exciting time for dual band/ narrow band as the competition between filter manufactures seems to be hotting up. IDAS, Baader, Astronomik and maybe others have released new products in the last year aimed at fast systems like the 135. Cheers, Des

Testing out the IDAS NBZ dual band filter. Samyang 135@f2 18 x 300s with ASI2600MC and ZWO EOS filter drawer. Further details at https://www.astrobin.com/users/desmc/

To mount the ZWO EAF I mostly followed the excellent design here: https://www.thingiverse.com/thing:4761672 Big thanks to Dale. Please note that I found I had to scale everything up by 2% and then used electrical insulation tape to shim the focus ring. This may depend on the vagaries of the 3D printer used. Dale's design is particularly nice as it allows the belt tension to be adjusted easily by moving the EAF in or out. All seems to work well with the ASI AIR - attached is the very first auto focus run. My back spacing currently is 27.3 + 17.5 mm (ASI2600MC) with infinity focus just to the left of the L (with an Optolong L Pro in place.). Should I add another 0.2mm? Please advise. Stars are not completely round in the corners, mainly bottom right. Tilt? Might be hard to tune out so probably best not to look! Thanks to everyone for help along the way. Des

Hi John, I am in the process of mounting my lens using essentially the same 3D printed kit you provided the link to. One difference Is that I use the Astro Essentials adapter, connected with appropriate spacers to a ZWO filter drawer and my ASI2600MC Pro. I also am having the riser fabricated in aluminium rather than 3D printed. What has been your experience using it? Am I wrong to assume that it is not positive if you are thinking of changing to a different mounting solution. I have very limited experience so far just using the WO Redcat ring, but this seems reasonably stabile to me. Cheers, Des

Thanks. Forgot the details. 30 x 120s lights, gain 100 -10C @f2 ASI2600MC Pro, L Pro filter. 50 x flats. 50 x Dark flats. Heavily processed in PixInsight, tricky because of strong light pollution, including heavy handed clipping.

Dear Adrian and Lee, Thanks for sharing your experiences. There's a lot of helpful info to guide next steps. Tuning the back focus is obviously the thing to concentrate on accepting at the outset that this will not be a joyful process. However, my approach will be to do this iteratively while imaging, as I still get a deep satisfaction in obtaining any kind of image, even one with bloaty red stars as in the attached! One very useful hint that might nudge me in the right direction is the answer to the following: If the optimum focus as measured by a BM is found to the left of the L (as looking skywards along the lens) does this mean that I need to increase or decrease the distance between the lens and the sensor? Currently at nominal 44mm, my focus is to the left of the L. Regarding the EAF, I like the look of this implementation: https://www.thingiverse.com/thing:4761672 or the one now available from deepskydad.com. I too am concerned about running out of adjustment if the focus is close to the hard stop. Best, Des

Hi Lee, Thanks. That is all very interesting and to the point. I too have the feeling that stacking exacerbates the issue, but only based on the few hours I have managed on a couple of targets and some half-baked analysis in PI. I intend to do some more testing clouds permitting. Next on my list is to fit an electronic focusser - ZWO EAF - to take out the guess work and fumbling. One quick question: how do you change the sampling in PI to go from 1:1 to 1:2. Do you use Resample at 50%? Cheers, Des

Sorry... Script -> Image Analysis -> FWHMEccentricity Run this having first separated your RGB image - if that is what you have - into R, G, B channels. Then select the channel to view, press Measure and then Support for the contour maps. The latter only works if it can find enough stars so need a sub of reasonable exposure length eg 120s. Cheers, Des

Hi Just getting started with my Samyang 135 and noticed that some stars have a noticeable red fringe. I've set my system up using the Astro Essential M48 adapter plate, and have set the back focus to be as close to 44mm as possible. Imaging time has been very limited due to clouds. To date I've only tried f2 with a OSC ASI2600MC Pro and an L Pro filter, focussed with a Bahtinov mask. Example image showing close up of stars with a red fringe. Using PixInsight, I get for the median FWHM and eccentricity in pixels for the different channels typical values of: R 2.037 0.6071 G 1.927 0.5880 B 1.857 0.6085 My questions are whether there is an issue with the lens, is it a focus and or back focus issue, or is it a consequence of shooting at f2? Thanks in advance, Des

https://pixinsight.com One of the most popular astrophotography programs for pre and post processing. For many people including myself it is a one-stop shop that does everything I need. Steep learning curve, worth it in my opinion, supported by many excellent video channels on youtube. Best, Des

Pixinsight Best, Des

Hi Pierre, BM finally arrived. I paid about £10 including shipping. It seems to work reasonably well, and the construction quality is reasonable for the price. Attached is a comparison of its performance against one acquired from the very helpful Lucas at https://astrojolo.com. The star I believe is Polaris. The images were taken in quick succession, first the one from aliexpress, and then the one from astrojolo. The fact that the focus was a little bit off seems more evident in the latter, which will be my first choice going forward, but both seem to perform well.

Thanks to everyone who has posted in this thread so far, as it has all been very helpful in putting together my rig. I thought it might be helpful to others to share some of my (limited) experience so far, and to ask for comments on whether the performance of my 135 is in keeping with what one might typically expect. First a few words on the rig: - I opted for a Redcat 51 mounting ring as suggested by many others. This seems to hold the lens nice and snug and my preliminary assessment is that it is a good choice. - The Astro Essentials M48 replacement plate was easy to install and seems well made. - As I am using a ZWO filter drawer (21mm optical path length), and an ASI2600MC Pro (17.5 mm back spacing required), I decided to use an M48 extension tube to get me to the required 44mm. First attempt was to try the Astro Essentials extension tubes available from FLO. This turned out not to work particularly well as the female thread on the extension tubes were not deep enough to take the male M48 thread on the lens plate. A better option seems to be to use the TS M48 5mm extender (https://www.365astronomy.com/ts-optics-2-inch-extension-tube-with-double-sided-2-inch-filterthread-5mm-length). This gets me very close, within a 1mm, of the required back focus with everything nice and firmly attached. First light was (surprise, surprise) the Orion complex as shown in the image: f2 21 x 120s lights, 50 flats, 50 dark flats, gain 100, -10C sensor temp. I am delighted with the result at f2, with perhaps the focus being a little soft. Looking at the variation of the FWHM and eccentricity it is difficult to know whether the lens is performing to spec (me, the imager, most certainly is probably not) so constructive feedback welcome. Thanks in advance, Des

Thanks, Pierre. It would be rude not to buy it at that price. I've ordered one and will report back on how it performs - it will take a while to arrive. Any thoughts on using a 77mm clear filter to protect the lens? Cheers, Des

Hi Pierre, Interesting suggestion - I'll look into it. Never knew such things existed but then again this hobby is an endless sea of discovery (and expense) spreading out in every direction. (I watched too much Carl Sagan as a kid.) Unrelated issue - is it a good/bad idea to think of putting a clear 77mm filter in front of the lens to protect it? Thanks, Des

Thanks, Carole. I've not come across this company before. Impressive looking performance. Best, Des

Thanks for pointing this out, Pierre. I have a WO clear Batinov mask on my z73 and they are indeed superb. Shame it is just a bit too small to fit the 135’s dew shield. As you wrote, probably a good investment given its versatility. best, Des

Thanks for the helpful replies. I decided to follow your good advice and skip the rotator to begin with. Managed to get everything mounted and aligned this evening - having taken delivery of the lens from amazon around 16.00 - and big surprise, the clouds rolled in even though the forecast was for a clear night. Snapped m42 and m45 through the high clouds anyway as an act of (futile) defiance. Can anyone recommend a Batinov mask, please? Either to buy or to print. Various designs are advertised but not sure which ones work well. Cheers, Des

Hi I'm setting up a wide field system based on a samyang 135 and have read this thread with interest. I've ordered the Astro Esstials M48 plate from FLO and I am currently trying to decide on the optical train between it and my asi2600mc pro. One option would be to use the combined rotator/filter holder from TS: https://www.teleskop-express.de/shop/product_info.php/info/p12074_TS-Optics-Rotation-Adapter--Filter-Holder-and-Quick-Coupling---M48-to-T2-thread.html For those of you using it I'd very much like help with a few details: - Does this screw directly onto the Astro essentials adapter plate? - Is the total optical path length of the combined rotator/filter holder 19mm with the filter holder in place? - For the asi2600 which has a tilt plate meaning that 17.5 of the stated 44mm back focus of the AE adapter plate is taken. This would suggest I need a 7.5mm T2 extension piece, as 44-17.5-19=7.5mm. Is this right? Finally, I wonder a rotator is really necessary at all as it might be simpler to loosen the WO ring I will be using and rotate the lens. In which case, I would skip the rotator and use a zwo filter drawer (m48/m42, 21mm optical path length) I already have, and make up the remaining 5.5mm with an m48 - m48 extension tube. Does this make sense? Thanks in advance from a relative newbie (started in this game last July), Des