I am trying to figure out backspacing with different filters. I've used IDAS filters and it seems that 1mm spacer works well. I recently purchased some astronomik filters but my stars changed for the worse. I have used an optolong clear focusing filter as well. Same results. I am wondering how people are spacing their hyperstar from the filter drawer? I know that the idas filters are thinker, 2MM I believe. What spacers are people using with 1mm thick filters? if any?
Hyperstar 8
Hi there,
If you ordered the Starizona filter drawer for Hyperstar, that should have come with the standard adapter for proper back-spacing. Direct from the manufacturer, the back focus for Hyperstar 8 v4 from the mounting thread to focal plane is 39.8mm. See this site:
https://starizona.com/blogs/tutorials/hyperstar-specifications
The critical focus zone on Hyperstar is *really* small (l think on the order of microns), so I only ever used the spacers directly from Starizona. The only filters I had ever used with my Hyperstar were the Optolong L-eNhance and the Baader f/2 Ultra-highspeed SHO set. Those all worked fine. The Baader set was 2mm and the L-eNhance was 1.85mm. Those also worked with the Hyperstar because the L-eNhance had wide bandpass so the bandpass shift from f/2 didn't matter, and the Baader set theoretically are pre-shifted to account for the bandpass shift. I'm not certain whether the bandpass shift would translate into change in star shape though.
If you are using standard Starizona filter drawer and their spacer, did you try recollimating the Hyperstar? I would do that first and then use something like CCD Inspector or ASTAP to check for tilt. Even the slightest tilt on Hyperstar will throw everything off. Lastly, are you certain you aren't dealing with a funky-looking diffraction spike from how you have your cables managed in front of the corrector plate? I tended to keep mine at 90 degree angles to get a nice cross-shaped diffraction pattern, but others have advocated for semicircular approach to cable management to avoid spikes altogether.
Clear skies,
Ben
If you ordered the Starizona filter drawer for Hyperstar, that should have come with the standard adapter for proper back-spacing. Direct from the manufacturer, the back focus for Hyperstar 8 v4 from the mounting thread to focal plane is 39.8mm. See this site:
https://starizona.com/blogs/tutorials/hyperstar-specifications
The critical focus zone on Hyperstar is *really* small (l think on the order of microns), so I only ever used the spacers directly from Starizona. The only filters I had ever used with my Hyperstar were the Optolong L-eNhance and the Baader f/2 Ultra-highspeed SHO set. Those all worked fine. The Baader set was 2mm and the L-eNhance was 1.85mm. Those also worked with the Hyperstar because the L-eNhance had wide bandpass so the bandpass shift from f/2 didn't matter, and the Baader set theoretically are pre-shifted to account for the bandpass shift. I'm not certain whether the bandpass shift would translate into change in star shape though.
If you are using standard Starizona filter drawer and their spacer, did you try recollimating the Hyperstar? I would do that first and then use something like CCD Inspector or ASTAP to check for tilt. Even the slightest tilt on Hyperstar will throw everything off. Lastly, are you certain you aren't dealing with a funky-looking diffraction spike from how you have your cables managed in front of the corrector plate? I tended to keep mine at 90 degree angles to get a nice cross-shaped diffraction pattern, but others have advocated for semicircular approach to cable management to avoid spikes altogether.
Clear skies,
Ben
Well Written Helpful Insightful Engaging
Hello thanks for the reply! I seem to have some sort of astigmatism with the Ha filter. With the idas nbz i have fairly good stars to the edges with 1mm spacer between the filter drawer an the 11mm spacer that my 294mc/mm is connected to. I am getting seagull like stars in some corners which would lead me to believe collimation is out. I have ordered a tri bathenov and a duncan mask and i will play with collimation. I have been using pixinsight to check my images for fwhm. I will try astap after i collimate. I have just heard of people using shims to get fairly good strs to the edges.
I would suggest trying Metaguide for in-focus collimation too. I have a Tri-Bahtinov mask too, but it was tricky to use. Once you get the hang of Metaguide, it's stupid simple.
Best of luck!
Best of luck!
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