Spongey

Amazing data as usual! Great fun to play with; I settled on a standard SHO combination in the end. I created a synthetic luminance channel from the three NB channels, weighted towards Ha.

Processed in Pixinsight and Adobe Lightroom.

My lum processing workflow from Pixinsight history explorer can be seen below. Happy to answer any questions on my workflow, please ask!

Cheers

After six weeks of bad weather we finally had a clear night so that I could finish this image!

This is a two panel mosaic of the Veil nebula in HOO, taken over five nights. My stars are a little wonky in some corners as I didn't have AF for the first four sessions, but that is solved now and future images should have good star shapes across the frame.

Panel 1: 
Ha - 48x 300s (4 hours)
Oiii - 81x 300s (6.75 hours)

Panel 2:
Ha - 48x 300s (4 hours)
Oiii - 57x 300s (4.75 hours)

Total exposure = 19.5 hours

This is first light with my APM LZOS 105/650 and I'm pretty pleased with it to say the least!

Constructive criticism is welcomed

Cheers

A second attempt that's not quite as stretched, in retrospect the first version was far too bright.

My take on this fantastic data! Took me quite a few tries to get something I was happy with, especially with the colour data, but settled on the below. I tried not to over-sharpen or make it 'pop' too much; I wanted to keep a natural looking process, despite the fact that the data can handle being pushed really far.

Ha was incorporated into the Red and Blue channels using this method.

Processed in Pixinsight and Lightroom.

Cheers

13 hours ago, RobST said:

I know this is a very old thread, but I'm just starting on a similar adventure, i have a 6d and have done all my imaging so far with a samyang.

I now have an eq6 mount on the way and trying to decide what telescope to stick on my 6d, my first choice is the esprit 100.

Did you stick with this combo long?

Judging by this image you had success with the combo as well?

Cheers Rob

The Esprit 100 is a fantastic scope and works well with the 6D. The corner stars won't be perfect but you can crop in a little bit to 'fix' that. 

Unfortunately my Esprit 100 had significant pinched optics in the cold and developed a mechanical issue too, so I ended up returning it. I was definitely very unlucky in this regard though; the vast majority of people who use this scope do so with no issues at all!

Cheers

Nice images! A shame about the halo in Oiii, I think a lot of folks were hoping that these filters would be halo-free. 

I suppose that will remain a characteristic of Astrodon / Chroma for the time being!

Thanks to the lack of astro-dark I've been sticking with narrowband imaging on the recent clear nights, which has been rather successful despite the non-perfect sky conditions.

The following image represents ~9 hours of SHO data split evenly across the three channels. As I am manually focusing and don't fancy staying up all night doing so, each filter was shot on a separate night. This allowed for a decent amount of time per channel, though the Sii and Oii data had to be noise reduced pretty heavily. Thankfully these channels were only used for colour data, with the exception of the small portion of calamari in the bottom right corner, which was worked into the otherwise Ha heavy lum. Not my best framing I will admit, but I was mainly interested in the central object for this one. 

Processed in PixInsight and Lightroom, with the following pixelmath formulae for the colour channels:

R = Sii*.6 + Ha*.4

G= ((Sii*.6 + Ha*.4)*.3) + ((Ha*.2 + Oiii*.8)*.7)

B= (Oiii*0.8 + Sii*.2)*.5 + Ha*.5

Taken with my Samyang 135mm at f/2.8 and QHY268M.

Constructive criticism welcomed!

A little update on my Samyang adventures! After almost a whole month of rain we've had some clear skies so I was able to get out and take some Ha data on IC1396. Losing astro-dark last week isn't ideal but I have found that narrowband in nautical dark / astro twilight is still acceptable (particularly towards the middle of the night). This is 3 hours from the other night:

The framing isn't the best but I was only aiming for the central target. I've included the full frame to show people what can be expected with this camera/lens combo!

54 minutes ago, AstroComet3 said:

Fantastic shots! Can I ask for a photo of the spacing you used with the Esprit 120 and the 268M? I'll be getting the camera soon, and from the end of my field flattener have an M48 thread but the 55mm back focus configuration ends in an M48 thread, and I would appreciate some clarification!

My image train was (I no longer have the Esprit 100): 

Field flattener with M63-M48 adapter (included with flattener, sets backfocus as 55mm from end of m48 piece) -> 1mm M48 spacer -> QHY M54 to M48 adapter (included with camera) -> 20mm spacers (included with camera) -> QHYCFW3M-US -> QHY268M

Back in mid-March, and after a few months of scope and filter issues, I had just about reached the end of my tether when it came to poor QC from non-premium astro products. As a result, I ended up putting a pre-order in for an LZOS 105/650, with a waiting time of ~4 months, and a couple of Chroma NB filters.

To tide me over in the mean time, I set up my Samyang 135mm f/2 lens and QHY268M for some widefield imaging. However, being in the middle of galaxy season meant there wasn't much to shoot, especially from my moderately light polluted back garden. One clear night, for a bit of fun, I set up my sequencer to start taking subs on NGC7000 when it rose at around 2am, not expecting to see much at only ~15 degrees altitude. I focused the lens and went to bed without particularly high hopes.

I woke up the next morning to see that my plate solver had failed, and the framing was a couple of degrees out. From the first few subs it was clear that this was because the target was partially behind a tree, and didn't rise above it until around 20 degrees altitude. The sequencer had continued through this failure though, and taken subs throughout the night with the odd framing. The later subs looked good, and I stacked them on a whim to see what was visible. I was impressed with what I saw, but unfortunately the framing had left me with an unusual field of view where the pelican nebula had been chopped in half.

After some deliberation, I decided to look at it as an opportunity rather than a setback, and aimed to expand the FoV by producing a two panel mosaic. The next clear night gave better results, with my plate solving issue resolved, and I managed to stitch the panels together without too much trouble. However, the resulting framing left a bit to be desired, with a strange aspect ratio, and not much going on in the right hand panel. I took to the Digitised Sky Survey to see what else was around, and discovered was that I was missing out a lot of interesting structure in NW Cygnus that I could fit in with a three panel mosaic. I also saw that I could fit in the crescent and tulip with a 3x2 mosaic... You know where this goes  

At the start of all this I only had an Sii filter, with Ha and Oiii waiting for production. A long lead time on these two filters, coupled with an amazing run of clear skies in April meant that I ended up capturing 3-4 hours each on eight (!) panels in Sulphur before I got the chance to dedicate some time to the other channels. As those of you who have done it know, working with an eight panel mosaic is no mean feat, and my computer struggled a lot when trying to process the data. At many points I felt like I had bitten off more than I could chew, but persevered regardless. That eight panel mosaic is currently sitting on my hard drive awaiting some Ha and Oiii data to combine it with.

In light of the imaging time required, and the huge processing overhead, I ended up settling for a three panel mosaic with the potential to capture more, weather permitting. Once my Ha and Oiii filters came in, I focused on those channels, and despite the nights getting shorter and shorter, I managed to capture 3-4 hours per channel in each of the three panels. With the current forecast, it doesn't look like I'll be getting any more data before astro-dark is up for the season, so I sat down and started to process what I had.

I did four full processes from scratch on this data before ending up with something I was happy with. Even now there are things I'd like to improve about the image, such as a way to incorporate more Oiii into the luminance; there is a large SNR in the right hand panel that I'd like to highlight a little better if possible, and some small PNs that could stand out more. Regardless, I'm very happy with the result and am going to call it finished, at least for now. Maybe after the summer or next year I will return to this and expand it to cover the full 8 panels in all three channels. 

The final (for now) image is as follows, and represents a 50% downsample on the full resolution mosaic.

Total integration time is approximately 36 hours, with ~12 hours per channel, split evenly among the three panels.

All data was captured with a QHY268M and Samyang 135mm f/2, riding on my CEM40.

Colour palette used was from this tutorial, with some tweaks.

Pre-processed in PixInsight, panels stitched in APP, and post-processing in PixInsight and Adobe Lightroom. 

CC welcome as always!

Cheers

9 hours ago, Adam J said:

I think it's ok to expect no pinching at 0c but -10c?

I would generally agree with this statement, but it has been shown in this thread that the Esprit scopes can, and have, pinched at temperatures above 0c. 

I mirror your sentiment with regards to engineering quality though; the Esprit line are known for their price to performance ratio, but I don't think anyone is claiming that they are in the same league as premium refractors.

They can and do get close to the results produced by premium brands in favourable conditions, but when pushing those limits, it is unsurprising that the Esprit falls down first.

On 23/04/2021 at 15:48, cfinn said:

Hi all, just thought I would share an update on this. The replacement unit arrived this week. All in excellent working order, except for the focuser which couldn't hold any weight. I found the four grub screws underneath the body of the focuser that control the focuser tension and a couple of them had become a little loose from shipping. I tightened them up gently and all is now completely fine. The dew shield assembly on this unit is also better than my last. It slides along the tube much better and does not sag as much as the previous one, so that is a bonus. Those blue shock absorbing balls in the case also stay in place a lot better!

I had clear skies and temperatures of 4C ambient last night, so I took the opportunity to do a quick test on a bright star (Capella). A visual star test at high magnification looked good - collimation spot on and nice even energy in the diffraction pattern either side of focus. I also used this as first light for my new QHY 268M with a single 30s exposure in luminance. The stellar halo is not free of artefacts, but I think that is to be expected for a star of this magnitude. It looks reasonably well controlled, and the stars across the rest of the field appear perfectly round with nice clean halos. So, for the time being I am satisfied. The real test of course will be next Winter season, but right now I am just pleased to have a telescope back to enjoy using once again. I purchased a Herschel wedge as well, so I can get some good use of it during the summer with some solar observing.

Charles

Looks like a decent test Charles! There is definitely some structure in the halo which looks like it could be the six-spoked collimation screws, but it's a very acceptable result. The real test (to me) is the smaller stars, once they start distorting and all looking like hexagons, as in my images, then it's not acceptable.

I'd be interested to see a defocused star test, if you could perform one; if you can see any notches in the edge of the star halo in these then that is indicative of pinching, and will be more visible than in-focus images.

This does seem to be a design issue with the Esprit lens cell, and appears to have been more prevalent in production runs over the last few years. 

1 hour ago, Wretmo said:

Astro Sweden warned me about this problem and told me that I am on my own if this occurs. I then contacted Optical Vision to check what support and help I could receive, and they let me know that they would replace any faulty telescopes. After confirming with Astro Sweden I ordered the telescope.

Today, five days later, I was contacted on this issue again by Astro Sweden. They had further discussed this with Optical Vision, and the message now was that the warranty will not cover pinched optics in low temperatures. No operating temperature range is given. "Low temperatures" is the normal condition for the astrophotography-season in Sweden. I was given the option to cancel the order. Makes me unhappy, seems to be an excellent telescope otherwise.

That is most disappointing of OVL. They clearly acknowledge the problem but are not willing to do anything about it. As you say, the Esprit is an otherwise fantastic scope.

33 minutes ago, Xiga said:

Thanks for the spreadsheet, very kind of you to share that with us 🙏

Can i just check something please - should the 2nd line above actually read: Gain 100 for ZWO = Gain 56, mode 1 (High gain mode) on QHY ?  

No problem at all! I didn't make this spreadsheet, someone on CN did so thank them instead!

Oops yes, good point. I will edit the original post

Just now, teoria_del_big_bang said:

This is a stack of 5 Ha subs from last night, same as you they are totally uncalibrated and I am now a bit worried about the amount of hot pixels I have.
I probably have not noticed these so far due to pre-processing my previous images that will have masked these.

You can clearly see many hot pixels that are made cleared because of the dithering. Does this look normal or should a new camera be better than this ?

Steve

 

I personally wouldn't worry about hot pixels in uncalibrated images. If you have a few hot pixels remaining in a calibrated sub then that is fine, and is what dithering and pixel rejection algorithms are for.

20 hours ago, tooth_dr said:

Sorry to bother you again!  I'm trying to figure out the spread sheet.  The 2600 high low gain conversion is 100, and 56 for the QHY.  But then I read below and it says when using mode #0, the gain conversion is 26? **EDITED - I  am now not sure what mode I've been using lol*

 

What effect is there on the figures in the spreadsheet for the QHY camera if the gain conversion point is different to the ZWO?

 

"

#0 Photographic Mode

This is the standard “default” capture mode. There is a high/low conversion gain cutoff point between gain 25 and 26 where you will see the read noise drop from about 5.2e- at gain 25 to around 2.5e- at gain 26. The read noise response is quite constant from gain 0 to gain 25, and again from gain 26 to about 60. Due to this, most users will probably want to use either gain 0 or gain 26 and nothing in between, as you would only be losing fullwell capacity and dynamic range in the middle. I mainly image at fast focal ratios of f/2.2 so for me it makes more sense to use gain 0. Users of slower focal ratio telescopes, or in dark skies, will most likely want to use gain 26 to take advantage of the lowered read noise. Increased exposure time is going to be recommended over increasing the gain into the “middle ranges.”

#1 – High Gain Mode

This mode features a consistently lower read noise throughout its response, with the tradeoff of a slightly lowered fullwell capacity. Like #0 Photographic Mode, there is high/low conversion gain cutoff point. For this mode the cutoff is between gain 55 and gain 56, where the read noise drops from approximately 3e- to 1.5e-. I like this mode the most for narrowband imaging as you can take advantage of the extremely low read noise at gain 56 without having to worry much about fullwell capacity. For most of my standard broadband imaging, I also prefer the lower read noise of gain 0 and still relatively high fullwell of 60ke-. Unless I am shooting a field with very bright stars in it where the higher fullwell capacity of Photographic Mode may be a better choice, this mode is my main choice for imaging with my RASA. This mode also features the best dynamic range at 14.26 stops.

"

The only two useful gains imo (for DSO imaging) for the ASI2600 are gain 0 and gain 100. Everything else you just sacrifice dynamic range for minor gains elsewhere.

Gain 0 for ZWO = Gain 0, mode 1 (High gain mode) on QHY.

Gain 100 for ZWO = Gain 56, mode 1 (High gain mode) on QHY.

The other modes for QHY are useful in some fringe cases, but the majority of applications are best suited to one of the two gain / mode settings above. Offset you need to determine for your own chip, but something like 20 is a safe bet if you can't be bothered to figure it out.

The spreadsheet can be operated from the first two sheets only, though only the first sheet is really needed for general calculations. Input your gear and sky conditions here: 

I have this set up for my Samyang 135mm, and 3nm Ha filter. For luminance imaging enter ~300 in the filter bandwidth cell, RGB enter ~100, and narrowband enter the bandpass of your filter. The LRGB values can be tailored to your specific filter set.

A transmission efficiency of 60% is used as a rough estimate of light transmission through your optical train, sensor QE etc.

Note that a desired swamp factor of 20 is excessive; a value of 10 is typically suggested (10 will leave only 5% read noise contribution in your final image).

The camera parameters located here can be changed to your specific sensor if you want, but the default ones are fine as sample to sample variation in these chips is very low. This section can be useful to calculate your specific skyflux and magnitude, if you wish.

The important output is this section:

This calculates, for your gear and sky conditions, what exposure length you need to achieve the 'desired swamp factor' from the first input section. The units are in minutes.

I have highlighted the only two important rows (imo), which refer to gain 0 and 100 (or their QHY equivalents).

The table also gives you the number of subs it would take for you to achieve the 'total integration time' from the first section, the corresponding dynamic range in bits, and the SNR. 

As shown, for 3nm narrowband in my skies with my setup, 9.3 minute subs are 'optimal' at gain 100 / 56 (for QHY).

Note that this calculator is ONLY useful from a perspective of determining sufficient exposure length to swamp read noise. Other factors, such as those mentioned above, could lead you to choose a different exposure time. For LRGB imaging you will undoubtedly want to shoot longer subs than the calculator suggests, or you will end up with a vast amount of files.

Hope this helps!

On 22/04/2021 at 14:34, tooth_dr said:

No I was just wondering about you saying about the need for pixel rejection.  I thought maybe you had a very small number of frames to work with.  But even at 600s, you would still have 25 subs, I would have assumed that was plenty for the rejection algorithm to work effectively.

Ah I see. Yes I opted for shorter subs for that reason as well as others, like less reliance on tracking / guiding etc.

With bright stars in the field I do clip star cores with 300s subs, but it's very minor. From a pure SNR standpoint I calculated (using this spreadsheet - for the ASI2600 but it's the same sensor characteristics) that I'm best off using ~9 min subs under my skies with my specific gear setup. However, the hit to read noise representation in the final image from using 5 min subs is only ~3% so I opted to use those instead, for the above reasons.

Cheers 

5 minutes ago, tooth_dr said:

Cheers.  I'll try the mode 1 tonight, and will go with 600s.  In the past I've been using 1200s subs along with calibration data, and this removed the bad pixels etc and dithering cleaned up what even was left.  Maybe you arent taking many frames in the mosaic?  You need at least 16 for the sigma clipping to work isnt that right?

I have been taking approximately 4 hours per panel in each channel so far, so just under 50 subs/panel/channel. I dither after every frame, calibrate with darks and bias subtracted flats, and this works excellently. As for the exact number for sigma clipping to work I don't think there is a threshold as such, but more is always better.

My master frames are very clean, I'd happily send one across to you for inspection if you'd like?

Cheers

Mode 1, Gain 56, Offset 10, 300s subs is what I use for narrowband, and it's been giving me pretty good results. 600s subs would probably be better but I'd rather take the small hit to noise and have more subs for pixel rejection to play with. I'm using 3nm filters for reference.

I'm not super experienced when it comes to NB imaging (this is my first mono camera), but an integration of a few hours has been enough for me to work with.

As I'm currently scope-less (although hopefully not for too much longer!), I've been using my Samyang 135mm at f/2.8 for imaging, but I did try the same settings at f/5.5 on my Esprit 100 before it was returned to good effect. I'm working on a widefield narrowband cygnus mosaic at the moment and I'm very happy with the results so far.

Cheers 

Fantastic data once again, and on a beautiful target. I found this one very difficult to process but after a few iterations managed to get something I was happy with

Processed in PixInsight and Adobe Lightroom.

Cheers

A little update to the NGC7000 mosaic...

Thanks to this great run of clear(ish) skies around the new moon, I've been able to catch about 12 hours of Oiii data split between three panels on the NGC7000 region! Plenty of really interesting objects in the frame, including several planetary nebulae and a large supernova remnant around the middle-right of the image.

I'm calling this channel done for now and moving onto Sii acquisition before the moon comes back too strongly. I've got ~4hrs on the left hand panel so far. I can only imagine what the full SHO mosaic will look like!

Cheers

An image born from tests with filters over the last few clear nights; my first ever colour narrowband image!

Very happy with the results considering this is only 2 hours in each channel, and the target sets pretty early in the evenings now  

Imaged with my QHY268M and Samyang 135mm @f/2.8. 

Happy to answer any questions about the setup or processing, so please ask if you have any. As always, CC is welcome!

Cheers

Caught some Oiii on the Rosette/Cone nebulae region last night to add to my previous Ha panel and here is the result! Very happy with this as my first ever bicolour image  

Cheers

Clouds rolled in late last night so I didn't get a chance to shoot any more of cygnus, but before it set I managed to snag ~90 mins on the rosette and cone nebulae! I've blended in a little bit of high res data on the rosette here, but it still looked great before that.

Cheers

23 minutes ago, Budgie1 said:

@Spongey how do you have yours mounted, are you using the 1.5", 1.75" tripod or is it on pier?

If you're using the one of the tripods, how is it for stability with your Esprit 100?

And how do you get on with PA and the bolts in the mount, is it an issue or just something you get used too?

Thanks.

I'm using the 1.75" LiteRoc tripod and it is solid as a rock (no pun intended). When I had the Esprit 100 I never worried about stability being an issue. 

PA is a breeze; I have the bolts just loose enough to be able to adjust them without using tools, but tight enough that they stay put after adjustment.

20 minutes ago, Daniel Karl said:

@Spongey Thanks a lot for chiming in and offering your experience! That sounds good indeed! The 'worst case' I could end up with in terms of Telescope would be a 152/900.
Weighing in at 8.5kg for the OTA only. Do you reckon, that'd push it?
And how do you feel about the iPolar?

A long, heavy refractor like that would probably be pushing it in terms of moment arm, especially for imaging. 

iPolar is fantastic, I'm typically polar aligned in <5 minutes.

I have a CEM40 (non EC model and before the G version came out) and I'm very happy with it.

I've used it with fully a loaded Esprit 100 and also with a FRA600 so far with no issues. Guiding is typically ~0.6-0.7" but has been as low as 0.5" on really good nights. Love the cable management too.

I personally wouldn't recommend the in-built guider version as it is quite limited in focal length.

Happy to answer any more specific questions you might have!