rsarwar

10 hours ago, FLO said:

More models are planned for StellaLyra and StellaMira but currently we are unable to share details. 

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? 😮

8 minutes ago, johninderby said:

I wonder if some that had been considering the Esprit 80 are now thinking about the StellaMira 90 after seeing these early results?

 

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. 

46 minutes ago, kbrown said:

I didn't really bother doing much with the focusing. I just set it manually to where I thought I'd see enough. I used this mainly for centring and aligning the secondary mirror on my newt after taking it out. Really handy for that. Then I used a laser collimator and a chesire eyepiece to fine tune things. Iterated the whole process a few times and I got a very good collimation.

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. 

9 minutes ago, rpineau said:

@rsarwar , which Arducam are you using exactly (they have a few ).

Do you have a link ?

Thanks

Rodolphe

 

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.

22 minutes ago, Chris said:

Thank you!  

Unscrewing the knurled M48 adapter on the camera side buys you an extra 5mm and reveals a 63mm male thread on the reducer/flattener.

The TS version appears to come with an additional adapter on the telescope side, whereas the StellaMira ends with another male M63 thread for attaching directly to the StellaMira 90 EDT.

I would like to do some full frame testing, I just need a full frame camera firstly.

I may look on MPB.com to see how much their most affordable Full frame is, hmm? : )  

Cheers

Chris

 

 

 

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 

19 hours ago, Chris said:

Another crack at the StellaMira data... The core was a bit blown out on the first rendition:

 

 

 

 

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

14 hours ago, kbrown said:

Good job! I've done something similar with my QHY5L-II and a CS mount CCTV lens attached to it. I used oacapture to view the video feed. It has a few different style reticles you can overlay on top of the image but nothing like in your software. Curious if you're planning to add support for any commercial astro cameras?

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

4 hours ago, JamesF said:

I have to admit that I wasn't aware of DIY electronic collimators at all, so "yet another" came as a surprise.  Interesting project though.

James

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. 

17 hours ago, Adam J said:

Pritty sure that as a rule the imaging circle is larger when you use a flattener than a reducer flattener?

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. 

4 hours ago, tooth_dr said:

@rsarwar I’ve exchanged them for the slower ones to use on an F4.8 scope, do you reckon they will be ok?

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

4 hours ago, tooth_dr said:

Would it be possible for my Takahashi Epsilon to be causing the filter to be off band?

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. 

On 04/08/2021 at 00:40, Xiga said:

Finally got a chance a couple of nights ago to have a very brief first light with my Qhy268m and the Baader 2" 3.5nm CMOS Ha filter (not the super fast F2 ones). 

Zero processing on this, just a stretch, not even cropped. It's just 9 x 360s so only 54 mins. I need proper calibration frames too, this has only had a very quick BPM and a single 500s dark (not even the same length lol) applied, together with some similarly badly calibrated flats! Time to finally get some decent calibration frames now i'm finally back in the game after a long 10 months out. 

I'm happy with the overall contrast and star sizes, but am a bit disappointed in the Sadr halo if i'm being honest. I wouldn't have been surprised to see halos in Oiii or Sii, but i was expecting the Ha to be virtually halo-free. In all my time using the 7nm Ha i never really saw any halos at all, i was really happy with it. I know Sadr is about as bad a case as it gets (annoyingly i never shot this with my 7nm) but what do you guys think, does it look ok or not? 

I also might have a slight spacing issue. Not completely sure, perhaps a tiny bit more spacing needed. Hard to say for sure, as immediately after the meridian flip i got 2 more subs before the clouds came in, but both had really eggy stars! I had moved my finder-guider to a dovetail on top of the SW 80ed (supposedly for better balance), but i think that may have introduced some diff flex, so i've moved it back again. Just need another test session on either side of the meridian to know for sure if it's ok now, then i'll move on to trying to get any tilt or spacing issues sorted for good. 

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

4 hours ago, newbie alert said:

Cough,  cough

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? 

On 25/06/2021 at 23:17, andrew s said:

The higher read noise in CCD cameras reduces the effective but depth so not a lot of difference but newer CMOS are 14 or 16 bit now.

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

On 27/06/2021 at 18:07, Mach13 said:

What now?  😮 can be controlled via USB? 😁 Amazing  I did not know that...  

What level of control can you have?  🤔

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?

17 hours ago, BCN_Sean said:

That's a beautiful project, something that I'll keep in mind as occasionally unpowered eq3-2's and the equivalent pop up around here for not a lot!

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.