First light AstroPhysics 110GTX

[gregbradley]

I received this a while ago and then it took a while to sort out the adapters needed to attach my camera and filter wheel. It's all working now, perhaps a tiny amount of adjustment still to do.

First light image is the famous Horsehead Nebula. Most of the data was well under 2 arc secs FWHM and a few around 1.32 arc secs which is the tightest data I have ever gotten. I out it down to the resolution of the scope and the good seeing I get down here at Sussex Inlet on the south coast of NSW (the ocean is only about 3 kms from me).

38 x 5 minute exposures. Bit of reflection happening from the filters. These filters are my earlier Astrodons as my other filter wheel needs the USB port replaced. It has the series 2 non reflecting filters. I expect those reflections to go once the correct filters are used.

Manually focused and piggy backing on my CDK17. Its 110mm aperture F6 native and with the tri compressor/corrector it gives F5 as used here.

Virtually no vignetting, I did not use darks, bias or flats. Subexposures were dithered.

I'll be adding colour to this soon.

Very happy with the scope. Check out the crop - can you believe that was taken with a 4 inch refractor?

https://pbase.com/image/175186620/large

https://pbase.com/gregbradley/image/175186630/original CROP

[Leo.G]

Wow!

[Startrek]

Greg,
You should be happy with the new rig , a great start , excellent image of the Horsehead. Some excellent fine detail with nice contrast too.
I’m trying to capture more Lum plus RGB to complete my Horsehead from 3 weeks ago ( HaLRGB )
My Obs Dome at Narrawallee ( 150m from the beach ) is powered up but that pesky cloud cover from the east just won’t move away. There is another band of cloud from the south due to arrive at 11pm so tonight might be a no go.
Monday night is 70/30 but Tuesday will be the pick , clear all night until the early hours. Fingers crossed !!
Cheers
Martin

[gregbradley]

Thank you. I am glad you liked it.

Greg

[gregbradley]

Thanks Martin.

Yes the clouds have been an issue for a while.
It can be annoying that it’s clear all day only to cloud up after dark.

Hopefully we are due for a decent run.

In the meantime I have a large number of images to be processed.
Spent a lot today getting all my software tools up and running on a laptop.

Greg

[PRejto]

Congratulations, Greg. Very tight!!

Peter

[Peter Ward]

Oh...that's very tidy indeed. A keeper of a 'scope for sure. :thumbsup:

[gregbradley]

Thanks Peter.Roland Christen has taken
APO scope building to the next level.





Thanks Peter. It definitely is a keeper.

Greg

[alpal]

Excellent result Greg,
it is such a wide field and all sharp from corner to corner.
The AP110 GTX is a magnificent scope.
Would you be willing to share your processing details?

cheers
Allan

[strongmanmike]

Hard to critically asses without knowing the processing but yeah, looking good :thumbsup:... of course, given the pedigree of the scope, we wouldn't expect anything less ;)

Hey, just had a squiz at your equipment album (https://pbase.com/gregbradley/astrophotography_equipment&page=all) too, you've sure had/have some purlers of scopes over the years :eyepop: awesome collection there, love'em all! :thumbsup:

Mike

[Bodon]

Crikey that's a photo! I think this week 'we' are in for a bad run of weather at night...

[AlexN]

Certainly looks befitting of its pedigree! Will be very interested to see it with some colour added.

I recently threw together 24x300s Ha subs of IC434 with my 120mm APO and it kind of blew me away. I've shot the target a LOT, with 3" refractors and 8~11" reflectors, but there really is something about the way a 4~5" APO renders the night sky that is truly breathtaking.

Looking forward to more!

[gregbradley]

Thanks Allan. Minimalist processing. No darks, flats or bias just dithered. Some Photoshop. Less is more.

The scope has virtually no vignetting. Although I probably should apply darks. Bias are not very workable with CMOS so I tend to stay away from them -even flat darks seem touchy. CCDs work well with callibration in comparison.



Thanks Mike. Yes I have some nice scopes. Sometimes I think I should thin them out but nah!



Thanks very much. It is a fabulous area to image. A tough one too with those super bright stars. I'd say these are the brightest stars in the night sky for imaging.



Yes a good 4 inch has a fair number of targets that look great in that format.
I am also looking forward to using it visually. My 130 is superb visually, very engaging for Milky Way cruises! I have read the 110 can take a lot of magnification without breaking down. I have yet to look through it visually but I will soon.

[Ryderscope]

That's very exciting Greg. Looking forward to lots of great images from the new set up.

[gregbradley]

Thanks Rodney.
Yes we can form the 110 - 130 club!

I have another image which is nearly ready to post.

Greg

[alpal]

Thanks Greg,
it's hard to know if you could squeeze some extra quality out of your images
by applying: darks, flats and bias frames.
It's been a matter of great controversy for many years now as per here:
https://www.cloudynights.com/topic/742186-sony-imx-455-camera-without-darks-and-use-dither-instead/

I suppose all you can do is try it and see if it's any better?
It would also depend on your stacking algorithm.
Your results are very impressive without all that mucking around.

cheers
Allan

[gregbradley]

If I get a large enough stack because they are dithered and each
Image does not have a lot of noise the stack is very clean.
But if my stack is not as large definitely darks work well.
I am finding flats to be a bit tricky and with virtually no cignetting not a lot of gain. Flat darks are hard if you do sky flats at dusk as the exposure length is constantly changing.

Darks are easy enough to apply. CMOS and bias don’t seem to get in too well.
Greg

[alpal]

Thanks Greg,
it seems you definitely know what you're doing
and you're getting top results.

cheers
Allan

[PRejto]

Hi Greg,

Not to argue a point too much, but from what (little) I know about CMOS cameras (my Player One Poseidon is quite new) there are more than a few guys over at CloudyNights that say the flat-darks are quite unnecessary with the newer CMOS cameras and that just taking flats in the normal way (just subtracting bias) will work just fine. I've done it both ways with my camera and so far I cannot see any difference.

Peter

[Startrek]

Greg,
I forgot to ask before and just out of interest, what camera are you using and what temp and Gain/offset settings ?
Thanks

Martin

[gregbradley]

Thanks Allan.



It would suit those who use illuminated discs for making flats as then you can control the exposure length to just one length rather than it shifting with dusk flats.

It's a bit of a trial and error approach as to what works and what doesn't.



Hi Martin, it's a QHY600mm and read mode 0 with gain of 26 and offset of 40. Ideally I would use 56 50 for narrowband but it starts to get too complicated as it requires its own set of darks etc.

[Startrek]

Greg,
Here’s an interesting document I found on the IMX455 sensor , well worth a read , if you have the time.
As with the IMX571 , the IMX455 sensor does exhibit random telegraphic noise RTN or 1/f noise ( salt and pepper noise ) which can be mitigated using Darks correction.

https://research.iac.es/preprints/files/PP23035.pdf

Even though it’s a minor problem and only visible when you zoom in and compare bright and darker areas of your image , I take the hard road and use the full calibration suite for all my images as I’ll do anything to improve an image even if it’s ok.

I also read somewhere that these sensors are prone to slight changes in QE ( negative output response ) after 12 to 18 months of use and that Darks are the only sure way to combat this deterioration which include warm pixels and RTN.

Full calibration suite
Darks from Library matched for Lights
Flat Darks for Flats

Using Flat Darks or Bias do not show much difference but I choose Flat Darks as a safe measure.

I capture my Darks library every 9 to 12 months ( I do it in my study ( darkened ) just with the camera itself and cap on , takes a day )

For Flats I use an LED light panel with dimming control and works a treat . The IMX571 in my 2600MM is very co operative ( I believe the IMX455 is as well ) and flats are quick to capture with during a session or after a session during the afternoon or evening.
I have no patience for Sky flats as your options are limited and variable.

Cheers
Martin

[gregbradley]

Thanks Martin.

Good to know your procedure.

I do use flats and darks on some images. If they work then great, if they don't I don't stress about it as there is more than one way to arrive.

I should get one of those panels. Not that expensive for a 110mm but getting up there for a 17 inch!

I do notice some odd effects using bias though. I'll make a fresh lot.
I basically have been only using 2 exposure times - 300 and 600 seconds.

The rain noise I have only seen once. It may have been diminished in the qhy firmware, I know the horizontal lines issue is reduced in QHY's firmware.

I imagine these are only problems if there aren't enough subexposures to get a decent stack and let maths get rid of the random noises by dithering.

I have some colour for this image, not sure if its enough exposure time though.

Greg.

[Startrek]

I use a Huion A2 LED light pad for my 10” Newt and a Huion A3 LED light pad for my 8” Newt

https://www.huion.com.au/product-page/huion-a2-led-light-pad

https://www.huion.com.au/product-page/huion-a3-led-light-pad

I just used black cardboard from Officeworks , cut it to the size of the light pad then cut a hole say 10mm wider than the diameter of the OTA. This reduces stray light from hitting the rig. Then slew the mount in Ra and Dec until end of OTA is pointing to Zenith, sit the light pad on top and take your Flats , very easy and convenient. I even taken them in during the day inside the Dome ( shutter down and door shut ) with a black large shower cap fitted over the back end of the primary mirror end to block out stray light.

I’ve had these light panels for about 5 years now and no issues at all , although the costs back in 2019/2020 were half the current prices.

Cheers
Martin