HD or no HD? or just affordable refractor

[liquidoice]

i have been with SLR photography for sometimes. I own a mid-high level SLR: 7D. thinking to get a decent telescope with 1 time purchase to go into astrophotog, for DSO, sometimes milky way, and moon, fit to be carrying around in my SUV. my region here is always cloudy and some area is misty at hill area. not easy to get a full clear sky. so fastar will really be useful.

I stopped my search now at CGEM 925 HD #11081 but is it worth it price?

the seller here quoted me a price of CGEM 925 HD #11081, which is 50% more than a C9.25-SGT #11046-XLT

the more i read, the more question i have.

a site stated that a refractor like this will also give a good astro image. i am confused. spending this much on either of this 925 SCT that is a few thousand, not wise?

Orion ED80 Telescope

SCT925HD should be better than newtonian f4 8"/10"? shorter, easy to pack and go to other location?

also, the reason i stopped at SCT925 CGEM HD, is the fastar features f2. light gather 25 times faster.

does it mean focal length 2350mm is also shorthen by 25 times? or how does it affect the focal length with fastar setting.

i was told there is another thing, focal reducer f6 for this. but for this model cgem 925hd SCT, appropriate focal reducer is not out yet. really? then how do i reduce focal length without fastar?

if i did get a CGEM 925 HD set, it comes with autoguiding in the main scope? does mean it mean getting a orion shorttube 80 guidescope with/without starshoot autoguiding camera, is unnecessary?

advice please. thank you.

btw, there is no one in my region, into this expensive hobby. i cant rely too much on telescope shop seller info. they are just trying to push as much purchase as possible from me.

pls help thx

[RobH]

I have the 11 inch Edge HD, and trying to get anything other than its native F10 is proving beset with problems as whatever reducer you use needs to be only a reducer, not a flattener, and needs to be at a very precise distance from the rear flattening element ion the scope. This means that you can't use a third party focuser such as a moonlite or Feathertouch with it if you want to use a reducer, as the reducer will change distance from the flattening element.

Imaging at F10 is a very tricky process, and not suitable for most DSO's, although for the moon and planets it's ok.

The Celestron reducer is now out for the Edge 11 and 14, but is around £600

If you want to use the Fastar facility, then the scope will be down to F2 and have a focal length of around 470mm.

At this focal ratio, focus is critical and the point of focus is tiny so you need to be using a computer controlled focuser to get decent results.

Also, collimation has to be spot on....any error here will produce poor results.

Also, if you want an SCT/Fastar setup, then the extra you pay for the HD scopes is wasted, as you're not using its flkat filed capability and it will be exactly the same as using a standard SCT.

My advice would be to go for a refractor based setup ....lots of targets to go for and much more forgiving

Rob

[perfrej]

I have the EdgeHD 9.25 and an FLT-98 refractor. Now, as for the 9.25...

It is a fantastic scope. There is a really god reducer from Optec, the Lepus 0.62x, which gives you 1457 mm focal length and f/6.2. Perfect for galaxies.

I also happen to own a Hyperstar 3 from Starizona. With that, you image at f/2.3, or 540mm. Recommended camera is the Starlight M26C for that setup.

You sure could get away cheaper with the normal SCT version of the 9.25, but I guess the optics are better in the HD, and you don't get to image at native 2350 should you want to do so.

It is an expensive scope, but the quality is excellent. You also get the benefit of covering 540 to 2350 mm of focal length with just one scope, albeit with some pretty expensive additions

Refractors are a different song all together. I love them, but you are basically buying just one focal length and a different kind of feel to the images.

If you do decide on a refractor, get a good one. If you are considering an Edge with additional stuff, you are obviously in the position to take a bite out of the wallet - get a Tak!

Whichever way you go, you will not be dissatisfied!

/p

[liquidoice]

I have the 11 inch Edge HD, and trying to get anything other than its native F10 is proving beset with problems as whatever reducer you use needs to be only a reducer, not a flattener, and needs to be at a very precise distance from the rear flattening element ion the scope. This means that you can't use a third party focuser such as a moonlite or Feathertouch with it if you want to use a reducer, as the reducer will change distance from the flattening element.

Imaging at F10 is a very tricky process, and not suitable for most DSO's, although for the moon and planets it's ok.

The Celestron reducer is now out for the Edge 11 and 14, but is around £600

If you want to use the Fastar facility, then the scope will be down to F2 and have a focal length of around 470mm.

At this focal ratio, focus is critical and the point of focus is tiny so you need to be using a computer controlled focuser to get decent results.

Also, collimation has to be spot on....any error here will produce poor results.

Also, if you want an SCT/Fastar setup, then the extra you pay for the HD scopes is wasted, as you're not using its flkat filed capability and it will be exactly the same as using a standard SCT.

My advice would be to go for a refractor based setup ....lots of targets to go for and much more forgiving

Rob

RobH, thx for the advice. I know what you telling me, learn to ride a bicycle first before i go driving a car. yes, i might end up some disappointment or difficulties. but i only have the budget and planning to buy 1 only telescope. and i wouldnt be buying 2nd telescope again, or sell off 1st scope to buy 2nd better scope. also, theres no one in my region i can possibly sell of to, for upgrading.

the fastar usage, focal reducer, are 2 more feature i wish to use the scope with, instead of stuck with same 2350mm focal length.

I guess you are using the cgem pro mount. can you fit your gear all in your car to another place? one of my local seller kept telling "dont go for giant scope (8/9"), u wont be able to carry it around." how portable / mobility for these setup?

I have the EdgeHD 9.25 and an FLT-98 refractor. Now, as for the 9.25...

It is a fantastic scope. There is a really god reducer from Optec, the Lepus 0.62x, which gives you 1457 mm focal length and f/6.2. Perfect for galaxies.

I also happen to own a Hyperstar 3 from Starizona. With that, you image at f/2.3, or 540mm. Recommended camera is the Starlight M26C for that setup.

You sure could get away cheaper with the normal SCT version of the 9.25, but I guess the optics are better in the HD, and you don't get to image at native 2350 should you want to do so.

It is an expensive scope, but the quality is excellent. You also get the benefit of covering 540 to 2350 mm of focal length with just one scope, albeit with some pretty expensive additions

Refractors are a different song all together. I love them, but you are basically buying just one focal length and a different kind of feel to the images.

If you do decide on a refractor, get a good one. If you are considering an Edge with additional stuff, you are obviously in the position to take a bite out of the wallet - get a Tak!

Whichever way you go, you will not be dissatisfied!

/p

thx for the advice, Perfrej.

i saw some ppl plugged their SLR to the front when doing fastar. you are using the M26C. this is much better than SLR? yea, i agree with you, i should be getting HD. flat image at the edge. if i cant get HD, i might as well better dont get into Astrophotog at all. get the best possible gear to get the best possible experience.

3 focal length option in one set of gear, thats what i am thinking.

btw, can i ask, how much time we need to spend to collect all the multiple long exposure for shooting, for different focal length in this setup?

i worry i cant spend the whole nite camping at remote place, and later get mob/rob.

1) fastar 1 hour?

2) focal reducer 1457mm. roughly how many hour?

3) original setup FL 2350mm, 4hr to whole night?

my region is always cloudy/rain, some area also misty due to pollution.

will this CGEM925HD stand better chance to get a good picture in city light poluted area or misty/cloudy area?

i think i am going for the CGEM 925 HD. i only worry they cant fit in to the back of my car.

the seller recommended me these items. are they any useful? should i get them too?

Deluxe Tele Extender

X-Cel 12.5mm Eyepiece

Ultima 5mmEyepiece

thx, RobH & Perfrej

[perfrej]

Well, f/2.3 is really fast. I hope I have this right, but if you shoot for one minute at f/2.3, then you need 7m 30s at f/6.3 or 19m at f/10 to get the same exposure saturation.

The comparison is not really fair because you would spend more than one minute and catch more faint whispy stuff, but none the less, it is extremely fast compared to higher f-ratios.

I know nothing of Celestron's mounts, though. I have an NEQ6 which barely handles the 9.25 with filter wheel, camera and guidescope (around 17kg), and a 10Micron GM2000HPS which can handle three of them stacked if need be. Besides, the 10Micron doesn't need guiding as it is really good at dual axis tracking and has a really advanced software for modeling the mount's errors in respect to the sky.

Whether the CGEM can guide good enough for full focal length astrophotography is, in my book, an open chapter... Someone fill that one in, please

I wouldn't stick a DSLR on the Hyperstar. It would probably add too much to the central obstruction - I think. The M26C is in-line with the original obstruction and doesn't add to it. For back side photography, i.e. at 1540 and 2350 fl, I would go for a monochrome CCD with a decent filter wheel, or a DSLR if you like those.

Tele extender on 2350 FL??? Why? Want to do visual on planets, perhaps...

You get a very good 2" 26mm eyepiece with the 9.25. I have used it twice for collimation, the rest of the time the scope has had cameras fitted. I do alignment, focusing, sometimes collimation, all with the camera. I also use the guide camera on the finder scope for the odd times when the first slew doesn't put the star on chip on the main camera.

So, short answer is:

1) Check the mount. Good enough for astrophoto?

2) Unless you're a visual planetary guy, skip extenders and eyepieces

3) Get a Baader Clickstop specifically for the EdgeHD 9.25

Good Luck!

Here's my stuff: http://stargazerslounge.com/discussions-mounts/179595-10micron-gm2000hps-operational.html