Here's 3 test shots I did in Ha Tuesday night. M8 (15min) , the Helix (20min) and the Tarantula (20min). All in 30s exposures. Calibrated and flat fielded. Lost focus as time went past. Next run I'll have to check regularly when slewing to different targets.
The C11 was fitted with my new toy, an Hyperstar 3 that reduces the C11 to F/1.8, that's 504mm FL for 11" aperture. The Lens is fitted directly on the corrector plate by removing the secondary. So the camera hangs off the scope front. There are pictures of the system here. I haven't collimated the system yet and all the shots were 30s unguided.
Not pretty pictures by any mean but what's interesting is the total exposure time on each object. A 30s exposure with this system is roughly equivalent to a 10-15min sub with my 5" newtonian.
You can actually see the core of the tarantula starting to burn already at 30s. When I have the whole rig collimated properly and I figure out how to guide it I'll be able to go deeper and minimise the noise.
If you are currently using an SCT, even as small as a C8 it's worth looking into those lenses. It will save you a lot of exposure time which is an added benefit with the weather lately. You can get a lot more done in less time.
This is certainly impressive Marc. An 11" F/1.8 system has super astrograph written all over it. The initial results do show promise given such short exposure times and arcsec/pixel sampling remains good. Do you have a 10nm or higher Ha filter? F/1.8 is quite a fast light cone that may cause a shift from the typically centered 656.3nm for Ha which would alter the filters efficiency (transmission). Not sure if you've done any research into fast astrographs, but there is some good reading here that describes the fast light cone concern - http://www.hbastro.com/Telescopes/Fa...derations.html
Would be keen to see traditional RGB results. Looking forward to seeing more of your imaging adventures with this gear.
Very impressive results. It would be well worth it to get a Hyperstar lens when purchasing an SCT, so long as the scope is compatible with the system (or able to be made that way) and not one of the newer ACF and R systems (by Meade).
This is certainly impressive Marc. An 11" F/1.8 system has super astrograph written all over it. The initial results do show promise given such short exposure times and arcsec/pixel sampling remains good. Do you have a 10nm or higher Ha filter?
No, I used the Baader 7nm Ha filter. The image scale is [2.87 arcsec/px], similar to my 5" newt at F/5 [2.475 arcsec/px]. With the QHY8 that gives me roughly a FOV of 2.5x1.2 degrees. It's nice and comfortable. You'll fit M42, the HH with nice padding around. Should be able to fit the whole rosette in one frame or the pleiades.
Quote:
Originally Posted by jase
F/1.8 is quite a fast light cone that may cause a shift from the typically centered 656.3nm for Ha which would alter the filters efficiency (transmission). Not sure if you've done any research into fast astrographs, but there is some good reading here that describes the fast light cone concern - http://www.hbastro.com/Telescopes/Fa...derations.html
Yes I did read up on this. Thanks for the link BTW. I'll check it out too. If you shine a bright light through a cardboard pinhole at the C11 primary you'll get a focused reflection back on the cardboard at approx 1520mm from the primary (secondary having been removed). With the Hyperstar 3 lenses assembly (approx 130mm in length) the CCD focus plane is located at approx 620mm from the primary. So the hyperstar shortens the light path by 900mm in that 130mm distance. So yes it's pretty steep and apparently causes different wavelengths to focus on different planes causing ghost images. Now the added benefit in that case is that I use an OSC camera. The OSC has a microlensing on the chip which further separates RGB in different pixel wells. So by "post filtering" the light you can choose to discard GB when doing Ha/Sii or only keep GB when doing Oiii if this makes sense. On a monochrome everything ends up in the same well and that's where the issue lies.
Quote:
Originally Posted by jase
Would be keen to see traditional RGB results. Looking forward to seeing more of your imaging adventures with this gear.
Yes me too. RGB is another beast altogether. I chose Ha for my first light because it's a no brainer from my location. Tight stars, no LP. Easier to "debug" and focus on the important stuff to start with. RGB will introduce another load of problems to sort out down the road. I need to collimate the C11 accurately now. We're not talking about "3 adjustement screws" on a secondary because in this case there is no secondary. So it's back to formula. Primary optical axis vs. baffle tube mechanical axis and tilt of primary and corrector plate. I found a really accurate method of checking this that involves a pinpoint light source and a laser dot. Will post when done.
Quote:
Originally Posted by renormalised
Very impressive results. It would be well worth it to get a Hyperstar lens when purchasing an SCT, so long as the scope is compatible with the system (or able to be made that way) and not one of the newer ACF and R systems (by Meade).
I think so too. Initial results show how fast it is to acquire data. Acquiring good data is another thing though. An old SCT can be converted with a kit to make it fastar compatible.
Quote:
Originally Posted by dpastern
As I said the other night Marc, wow. Such potential. I'd like to see what guiding + longer subs can do on fainter objects ;-)
Dave
I should be able to guide sometime next week. Getting bits and pieces now. I was guiding with an OAG on the C11 before so it's a bit hard without the secondary now.
Quote:
Originally Posted by sheeny
Great first light! Keep 'em coming. I'm following with interest.
Al.
No worries Al - will do.
Quote:
Originally Posted by alan meehan
Marc brilliant shots for 30sec wow,i just sold a c8 with faststar
on it to troypiggo maybe he should give it a try looking forward to more
Alan
Sigh... And I sold my C11 because because it was too longer focal length for me to handle at the time..
I hate my life haha
Awesome Marc...
Ps - Wanted - C8/C11/Meade 10" SCT
Yeah I recall you selling it. I got your Bathinov nask, remember? Silly silly boy!
Quote:
Originally Posted by peeb61
Marc,
I am wobbling in my boots! I can see the power this unit has to offer.
Great results for such short exposures...I want one!
Are they suitable for a 10" LX200gps? I suspect they are depending on the type of camera used.
Great work...I want to see more!
Paul
Hey Paul, they work on all the Celestron SCT including the new aplanic/HD range and they also work on the meades. Different fastar types for different apertures and mades. Wide range of cameras. Actually I reckon anyone who's got a DSLR and an SCT should have an hyperstar. You go deep in 2min max. Well before any Canon would start building any noise IMO
Yes I remember, and you're right.. it was silly of me to give up on the SCT... Severe moment of weakness... I am exceptionally happy with my TMB 80/480 though, and whilst I can see the awesomeness of the hyperstar C11, I don't think I could justify buying a C11 + Hyperstar for between $4000 and $5000 total, to have an imaging system with 20mm more focal length than I have now, just for the sake of it being F/1.8... Yes, it would make life easy, tri-colour narrowband images done in hours instead of DAYS etc.. I just couldnt bring myself to sell the TMB. and would find it horribly redundant to have two imaging rigs with the same focal length...
1- DSLR's and filterwheels will block too much optical path in 8" SCT. You need to be looking at a C11 or larger Hyperstar.
2- Some Hyperstars will not cover a large sensor - check before you buy.
3 - Starizona sell a conversion kit for the SCT if it is not hyperstar/fastar compatible.
4- For small objects a more conventional SCT + Flattener will still likely give better resolution and detail
I'll check it out too. If you shine a bright light through a cardboard pinhole at the C11 primary you'll get a focused reflection back on the cardboard at approx 1520mm from the primary (secondary having been removed). With the Hyperstar 3 lenses assembly (approx 130mm in length) the CCD focus plane is located at approx 620mm from the primary. So the hyperstar shortens the light path by 900mm in that 130mm distance. So yes it's pretty steep and apparently causes different wavelengths to focus on different planes causing ghost images. Now the added benefit in that case is that I use an OSC camera. The OSC has a microlensing on the chip which further separates RGB in different pixel wells. So by "post filtering" the light you can choose to discard GB when doing Ha/Sii or only keep GB when doing Oiii if this makes sense. On a monochrome everything ends up in the same well and that's where the issue lies.
An old SCT can be converted with a kit to make it fastar compatible.
haha
