ed80 v c8 edge hd with hyperstar for astro

[iwols]

any comments welcome,how would you use a mono ccd and filters with the hyperstar? or do you have to use a colour ccd cheers

[vlaiv]

Don't think C8 & Hyperstar is diffraction limited, so star definition will suffer somewhat.

You can use Mono camera with Hyperstar, but you can't use filter wheel with it - it will block too much of light.

Select narrow body CCD/CMOS camera so it does not create additional central obstruction (don't know how big CO is on C8, probably around 70mm, so most cameras with cylindrical body should be fine). You need to use filter drawer type of filter holder, or some sort of filter adaptation inside mounting rings (there is outer T2 thread 1.25" filter adapter that you can screw in T2 nose piece, I believe there are such filter step down adapters for M48 as well). There is pretty good solution to this in Baader Universal filter drawer (you can combine different parts for your mounting needs, and I think that body of it is a bit bigger than 2" filters, so should be around 70mm as well, and it is round).

If you are looking at fast system around 400mm for smaller sensor there are couple of options out there:

Takahashi epsilon 130 - 430mm

Boren-Simon 6" f/2.8 - 420mm

Good F/4 newtonian with ASA x0.73 CC - 6" will give you ~440mm  FL (go for custom made one with strong and precise focuser - you need to correct even smallest tilt for this to work well, and of course collimation).

Esprit 100ED + Riccardi x0.75 FR/FF

So depending on what you aim for, there are several different options to choose from. People do use Hyperstar on SCTs, and since you already have C8 edge - that removes quite a bit in terms of expenses. It is by far the "fastest" option out of listed on 400mm focal length scale. Question is, how much do you value sharpness in your images?

[vlaiv]

Just to add - you need different narrow band filters with such fast systems. With such fast beams, some of the light is hitting filter at quite big angle - and with interference filters that means shift in central frequency. If you use too narrow filters like 3nm - most of the light will be outside of the band of filter - so filters will not work good. There are special filters that have their central frequency adjusted and also allow for broader band to offset this problem of incident angle.

[iwols]

thanks its the edge hd if that makes any difference

[Star101]

Using filters with Hyperstar, one needs High Speed filters.

https://www.firstlightoptics.com/narrowband/baader-f2-highspeed-narrowband-filters.html

 

The filters can be fitted into a drawer between the lens and camera. Make sure you order the correct adapter for your camera. T48/Canon etc.

https://www.365astronomy.com/starizona-filter-slider-filter-drawer-complete-system-with-one-2-m48-filter-holder.html?gclid=Cj0KCQiA_s7fBRDrARIsAGEvF8ScJume23UST_19GYoxSbeNgC7_krt9NXzIxTldrrGhvwtRXLwYzIUaAnCaEALw_wcB

 

I have Hyperstar with my C11. It works great. Very fast f/2 imaging and quite a wide field of view....But not wide enough for some objects. (  My Canon 50D with fit M45 in one shot where as my ATIK 4120EX will not. )

So, I purchased a TS 65EQ Quad for a wider field of view. I can now image M45 totally...I could not fit M45 in filed of view with Hyperstar.

Field of view is down to chip size and pixel size. 

https://astronomy.tools/calculators/field_of_view/

 

So I guess it comes down to what you want to image, how fast and at what focal length.....Price might come into it somewhere along the line too

 

[vlaiv]

Here is a good thread over on CN - comparison between Celestron RASA 8" and C8" HD + Hyperstar (just text no pretty pictures):

https://www.cloudynights.com/topic/632361-celestron-rasa-8-or-edge-hd-8-with-a-hyperstar/

It looks like C8" HD + Hyperstar is very touchy system - you need spacing spot on, collimation spot on, all distances, focusing, everything spot on, and it still will not be diffraction limited - not because of C8 vs C8HD, but rather getting fast F/1.9 beam of of it - optics simply cannot correct it down to diffraction limited - there is some spherical aberration left in all but green wavelengths - this means fat stars - which may or may not be an issue.

Due to spacing requirements and backfocus on 414ex - you may need to go for simple filter screw in adapter - this means unscrewing camera to change filters / refocus. Focusing will be problematic (either moto focuser, or special bahtinov mask). Flats will be problematic - can't use standard flat box - probably needs some sort of "spacer" to get it to work as camera is in the way.

Since you are planing to use it with 414ex - I presume, you will be sampling at 3.41/pixel - don't know if this star distortion is even going to show at such low resolution. 8" at this resolution is going to be seriously fast

 

[ollypenrice]

The key thing is not to believe the Starizona publicity which suggests this system will make imaging easy. It won't. The excessively fast F ratio introduces a host of complications as has been suggested already.

Olly