rsarwar

I feel like i should hold off on the 90mm F6 and wait and see if there are more models coming out. maybe a 100 mm F5.5 doublet? 😮

I am seriously considering 90mm instead of esprit 100. Its sat on my FLO basket as I type Wondering if anyone tried it with starfield 0.8 Field flattener. Need the extra back focus. Ian at FLO suggests it will work, but wondering if anyone tried it and could comment of flatness of the field and also image circle. Because i dont think i be willing to sacrifice the flatness of the matched FF for extra back focus. Neither do I want to start taking flat frames

An alternative solution would be to connect the motor using time belts with some gear reduction.

I see. I guess that is the most tricky bit, however, If you are able to change the focus you should be able to do the whole collimation process without a laser. Like collamating with a Cheshire only. Saves you from ensuring correct collimation the laser collimator as well. I just used the laser to confirm that collimation worked.

This one: https://www.amazon.co.uk/gp/product/B07YHJK4LN/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 but i suppose you can also get the ones that are based MIPI, but that may require modifying the application. basically any camera that can have motorized focus would do and can be centred on the two inch would work.

Thanks chris. 5 mm is great as i got a wierd BF combo: QHY268 (12.5+1.8) -> M54 F (4 mm) -> M54 M to M54 M (2 mm) -> ZWO 2in EFW (20 mm) -> ZWO M68 (17.5) -> M68 F to M63 F (1 mm) = 59 mm. Have you tried using a OAG with a APS-C sensor. i think it should give you a good indication if the image circle is big enough to cover Full frame as well, because APSC diagonal + 8 mm prism would amount to 35 mm more or less? I was about to place an order when i spotted that FLO has a ex-demo RC on promotion as well. no i am so confused as if i buy two scopes at once, i will no be allowed inside my bedroom

Hi chris, great video. and great images. Looking at the flattener, it looks like it is a similar to the TS flattener that they put up with their 90mm f6. on one of the diagrams on the TS website, it is suggested that tthe M48 thread is actually on an extension which can be taken off. is that the same in the Stellemira flattener as well? if yes, what is the thread on the camera side once the M48 extension is taken out and how much does it increase the backfocus. i kinda need the extra space. :S Also, would it be possible to maybe upload a white using a full frame dslr or something similar please. Thanks

I could. Should not be difficult at all. However, how do you change focus on the Cs mounted lens? I have a ASI290mm with the c mount lens it comes with, but the reason why I got the camera for arducam is because we need to be able to change focus. This would allow you to correctly focus properly on the edges of the second art mirror to ensure that it is within the circular overlay. And then swap focus on to the image on the secondary mirror to fine tune the secondary and align the primary mirror. Ps: zwo publishes python drivers for their camera, so it will be straight forward indeed https://github.com/python-zwoasi/python-zwoasi/blob/master/zwoasi/examples/zwoasi_demo.py

I am sure someone must have made it.

I am planning to get a 200 mm RC scope but i hate collimation process on my newtonian. i tried lasers and a cheshire. whilst i am able to get fairly okay collimation following testing with a LED torch under a Al foil with a pin hole, the process usually takes hours. and the results were never fully satisfactory . then i saw a Ocal Electronic Collimator on FLO and thought it should not be difficult to make it using a Arducam + some python/openCV coding. So I 3d printed a 2 inch frame in which I screwed the camera. first impression, need to reprint the 2 inch frame in red, so that it is easier to see on the mirror. camera i chose is a bit expensive but works well. total cost was about 50 pounds for the camera. python codes and stl files are in https://github.com/rsarwar87/pyReflectorCollimator camera: https://www.amazon.co.uk/gp/product/B07YHJK4LN/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Just realized I have a spectrometer and a monochromator at work using which I could carry out the measurements needed to work out the transmission curves. I only have the ha 3.5nm f3 to f10. So I will try that when I get a chance get the spectrometer working again.

You are probably right. But I was testing the stellamira flattener on a 72ED and it did not allow me to use a OAG with a APSC camera. So the image circle was pretty narrow. Not entirely sure if that is because of the size of the apparture on the focuser or the flattener intake.

I only have the standard 3.5 nm Ha from Baadar. only used it with F5.8 and it works as expected. waiting for the current project about california nebula to finish before i try it on the F5. but i think F5/F4.8 should be dead easy for any filters with 3.5-4 nm passband given that the bandshift would be slightly less than 1 nm. Ideally, if you know what your blue-shift is, you cat get a filter with a bandpass twice that, and you should not have any issue with f-stops. That is why 12 nm astronomiks are rated to f1.8 (although i think astronimik OIII 12 nm is still F2.8(see screenshot) as their oiii passband does not have a flat top). Having said that, it is still possible to design a 3 nm filter to incorporate a 2-3 nm worth of blue shift with some clever pre-shifting techniques which is what Baader claims to be doing, Oiii @ f3 Ha @ f2 I ordered the astronomik 6 nm Oiii - i think that is the right choice as I am planning to get a SharpStar 94 (f4.4) sometime before xmas. currently deciding if i should get the antila sii or just go with 6nm astronimik.

Just had a look at the rated f stops for the high speed ones. f/3.4 to f/1.8. The blue shift will range from 1.5 (f3.4) nm to 4(f1.8) nm. That is very difficult to do, and unless the bandpass have a flat-top, which it is not based on the polish data. I don't expect it to work efficiently. Eg. If the filter has a max performance at f2.5, by the time it reaches f2.8, transmission will be reduced 60-70 pc and <50 pc by the time it reaches f3.4. This is what I am worried about. Baader is being unprofessionally liberal with their specsheet. Which is why they labeled their standard speed 3.5 nm filters as to having the same f stop rating as 6.5nm. I think they are taking a 50 or 60 pc transmission as an acceptable range

Unlikely. More likely that the bandpass not being correctly shaped or a faulty glass. Have you tried asking for a replacement to try? 2.18 refrective index is very hard glass, similar to artificial stones used to make jewelries. Somehow I am having hard time imagining those being used in this case. I could be wrong. I read in a different thread that you also own antlia 3nm. Can I ask if you tried that one with your f2. 8?

I cannot tell the reflective index from the plot, but a blue shift of about 4 to 5 nm is correct. I think that plot looks reasonably. But this plot is not correct for a glass with reflective index of 2!! So the question is is it really 2.18? https://www.cloudynights.com/topic/724945-narrowband-imaging-at-fast-f-ratios/

Does it work with the 1.x stellamira flattener? I appreciate it will reduce image circle as it is a m48 sized opening. I was thinking of the 94mm sharpstar, but this looks like it is in the same price range. Any chance of anyone knows how the two stacks up against eachother? The latter is slightly wider, and is at f5.5 when coupled with a 1.x flattener.

I asked @FLO if they have some transmission plots, but I don't think they have anything extra beyond what is in the public domain (was hoping they had a secret stash of datasheets ) I think I am going to go with astronomik or antlia and keep the Baader ha as mine seems to have no halo issue. I still don't understand how a 6.5 and 3.5/4 nm filters have the same f-ratio rating. Controlled Halos, I can live with, but not knowing what I am buying is just not my thing.

this is my sadr on 3.5 Ha on 72ED + QHY268M. i am tempted to say that the halo is more controlled for me. i am quite surprised to see such difference honestly. I am temped to go with astronimik 6nm honestly for Sii and Oiii. atleast for the Oiii. i think i am happy with the Ha honestly.

HI Anyone got a transmission curve of these filters? both 3.5 and 6.5 nm filters are listed to be working from F3.5 to F10. I donot understand how they both have the same range range; especially the Oiii. i would expect the 3.5 nm filter to have narrower profile. if someone has a transmission curve for these, i be happy to calucate the theoratical F limits. has anyone tried them with a F4.4 scope? Also wondering if the halo on the 6.5 nm are also as bad as 3.5 nm or not.

I use something similar to this. https://www.thingiverse.com/thing:3383422

I agree that CCD is better for photometry, but for imaging, cmos now have the same QE with lower read noise and well depth and same bit depth. Unfortunately I don't have any CCD so I can't compare the two using same scope and light pollution. So I cannot prove my statement with data. EDIT : did you decide if you wanna modd you cgem?

indeed, the 16-bit CMOS in QHY268M can outporm almost any 16-bit CCD .

you cannot really do anything much with the USB unless you get yourself a DSUB, use your snap port if you have one or make something to accopmish remote release control can i ask how much you paid for the camera and if it was astro modded?

My next plan is to make a real-time PEC for the mount. The idea is have a 2+2m multi-pole magnetic strip and use a AS53111 chip measure the rotation. it has a resolution of 0.5 micrometer. so should be able to run a feedback loop to the fpga to correct for periodic error. Only thing is i need to work out how to mount the chip on to the mount and also if i should run the feedback loop from the fpga or from the rpi. the correction latancy for running it on fpga is about 20 ms (5 ms if i dont use any smoothing filter), and latency for running it from Rpi will be about 0.5-0.6 sec which i fear is too slow but a lot simpler to implement. That is about 30-40 pounds worth of hardware and to imagine that a similar instument is sold by explore scientific for £1250 is mind boggling.