Testing a tamed C8 Hyperstar: IC1396 Elephant’s Trunk Nebula in H-alpha

[Ikonnikov]

After being less than satisfied with the sharpness of my Hyperstar images I decided to take a leaf out of Mike Hawtin’s book and slowed down my system with an aperture mask; I ended up using the outer portion of an old Bahtinov. After some hacking and filing this gave 160 mm diameter and although it was somewhat painful to sacrifice precious aperture, the decrease from F2.1 to F2.66 seems to be paying dividends. In addition to increasing the critical focus zone (from ~14 to 23 microns for Ha with my setup) the aperture mask had a substantially reduced star sizes; in Nebulosity 3 focusing I was able to go from HFR values of ~1.55 down to ~1.15.

To test out the setup I took a number of Ha subs of IC1396 over the last week and was quite encouraged with the improvement in the image sharpness in spite of the nearly full moon and poor transparency. The brighter stars are still a bit of a mess but I think this might be due to a combination of my lack of processing skills and the (unavoidable?) reflections generated by the Hyperstar.

As ever there are still more things I’d like to try to see if I can further improve image quality (in addition to better processing). I’ve just invested in a JMI motofocus to speed up and hopefully improve focusing further. Also I used the Baader 7nm Ha filter here but appreciate below F3 this is going to let through a lot less light due to wavelength shift; I now have an Astronomik 12nm but haven’t tried this out yet (with the moon I though the 12nm might be asking for trouble). I see Baader are releasing NB filters specifically optimised for F2/Hyperstar so might have to try one of these out as well…

Paul

IC1396

C8 Hyperstar III on HEQ5 (Pier mounted, 60mm Finder guider with QHY5v)

Atik 428EX mono@-12C

Nebulosity 3 capture, PhD guiding

Ha 59x600s (Baader 7nm)

Pre and post processing in Pixinsight

http://astrob.in/full/120476/0/

Cropped Image:

[ollypenrice]

Very interesting indeed. Only rarely do Hyperstar images show anything like the resolution that they should for the aperture. Greek Anthony, much missed on here, was very successful with his but this has all the makings of an important refinement. This looks pretty tight.

Olly

[Ikonnikov]

Very interesting indeed. Only rarely do Hyperstar images show anything like the resolution that they should for the aperture. Greek Anthony, much missed on here, was very successful with his but this has all the makings of an important refinement. This looks pretty tight.

Olly

Thanks, the aperture mask really seems to make a difference even accounting for improvements in guiding/polar alignment since my earlier attempts.  I hope to try it out for some luminance subs when conditions allow and see how they work in LRGB with OSC subs taken at F2.1. There’s also the issue of whether I’m prepared to lose any more aperture in an effort to tighten things up further…

I’ve seen you mention Greek Anthony in some older posts but I don’t think I’ve ever come across any of his work. It does seem that most of the better Hyperstar images have been done with larger scopes (C11 and above) which I guess have intrinsically higher resolution and also allow a wider range of cameras to be used.

There is a German chap going by the user name ‘equinoxx’ who keeps getting Astrobin PODs with a C11 Edge HD Hyperstar setup and an Atik 11000 (which puts my tiny 428EX’s chip to shame!); as far as I can see he uses it at F2.0 but I don’t know if he has made any modifications, for narrowband he has preproduction samples of the Baader F2 filters.

Paul

[lensman57]

I am not a fan of Hyperstar but your full res image is full of detail, great image.

A.G

[Ikonnikov]

I am not a fan of Hyperstar but your full res image is full of detail, great image.

A.G

Cheers, I was beginning to arrive at the same opinion about the Hyperstar but thankfully a circular piece of plastic seems to be giving it some more life (and saving me £££ by postponing the purchase of a new Borg or TMB I was close to pulling the trigger on).

Paul

[ollypenrice]

You're probably right that the biggest Hyperstars are the best. The central obstruction possibly becomes less intrusive. This is a case of experimentation being the way, I guess.

Olly

[Ikonnikov]

Yes, I wasn’t quite sure what to expect when I bought it, but since the HS lens was only ~£300 second hand I figured it was worth a punt. And the experimenting is quite appealing being a scientist and all (not that I’d say no to a nice Takahashi Epsilon or FSQ if anyone was offering!).

Paul

[Ikonnikov]

OK I've added some OIII data to the image now (also taken at F2.66) http://cdn.astrobin.com/images/thumbs/9b3596626917f79c98cbe3eb8848ef87.16536x16536_q100_watermark_watermark_opacity-15_watermark_position-6_watermark_text-Copyright%20Paul%20Cordell.png

Unfortunately I've only managed to get about half the length of total OIII exposure (32x10mins) compared with the H-alpha (with seeing and transparency not great either) and the noise is relatively high. I've probably got bit carried away with Pixinsight's TGV denoise to counter this which has softened the image, undoing some of the good work of the aperture mask! So really need some more good quality OIII data to finish it properly.

Star halos are still pretty bad with OIII filter/Hyperstar combination and I've probably over-clipped the black point again (I blame my hyper-bright Samsung monitor!)  but overall I think it's sharper than my previous bicolour attempt at NGC6888.

Paul

[Earl]

You Ha  shot is great, id really hold back on the noise reduction in the bi colour its smoothnig out your detail.

[Ikonnikov]

You Ha  shot is great, id really hold back on the noise reduction in the bi colour its smoothnig out your detail.

Thanks Earl, I'm still getting to grips with TGV denoise; for the bicolour I used it after histogram stretching but I think I'll have a go on the linear images next time as this seems to be less brutal (some more OIII data still wouldn't go a miss either if the weather plays ball).

[Ikonnikov]

I've had a quick go with TGV in the linear stage and have also stretched things a little less to try to keep the noise down.

http://cdn.astrobin.com/images/thumbs/9f24a6464c04ef2901792a152f965adb.16536x16536_q100_watermark_watermark_opacity-15_watermark_position-6_watermark_text-Copyright%20Paul%20Cordell.jpg