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Old 17-06-2012, 12:48 PM
rthorntn (Richard)
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Lightbulb Newbie wants to do astro in Sydney CBD

Hi,

Please be gentle but at the same time tell me if I am crazy

I am looking to get in to Astro as I would like to have the scope GO-TO say a DSO and have a nice CCD capture it so I can manipulate it on one of my computers.

I am thinking of getting an 8" SCT (although would an astrograph be better) and a KAF8300, with the SCT I saw a tip along the lines of binning the KAF8300 2x2 would give awesome image resolution and would be a very clean, very sensitive camera with 100Ke well depth. I am interested in narrowband astro.

My budget is $4K to get everything I need, I am happy to order the smaller stuff from overseas to save cash, I see the ATIK 383L + CCD Camera ($1790 USD) and that seems to be in my price range.

So I would need a scope (it needs to be fairly compact/have a high WAF), any suggestions for this, any other bits and pieces, for example to attach the ccd to the scope also I understand monochrome is the way to go?

By all means please point me to any online guides that would help.

All advice on astro, urban, scopes, ccds, go-to and accessories is much appreciated.

Thanks for your time.

Cheers
Richard

Last edited by rthorntn; 17-06-2012 at 01:07 PM.
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Old 17-06-2012, 08:08 PM
roughy (Mark)
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Hi Richard

It's a bit problematical getting a camera. I too am a newbie and started accumulating imaging gear about 14 months ago. I received some excellent unbiased advice from a number of forum members.

Below please find the comments from one, Greg Bradley, that I found very helpful, if not a little daunting:


"I'll attempt to answer that.

First consideration should be your local seeing conditions and the focal length of your scope. The camera needs to be matched to the scope and seeing conditions.

Here is a free calculator which can work this out for you with different scope and camera combinations (the camera list is out of date but you can plug in the numbers):

http://new-astronomy-ccdcalc.software.informer.com/

What this means is for an RC8 of 203mm aperture and 1624mm focal length an 8300 chipped camera will give .68 arcseconds per pixel.

The 8300 chip has 5.4 micron pixels (smallish) and 3326 x 2504 in the array (or a number very similar).

Assuming average seeing of around 2-3 arcseconds (an arc second =1/60th of a degree ie. a pretty small angle) and assuming sampling theory is correct which states you want a minimum of 2X perhaps 3X times to get an accurate sample. Then you get 3 arcsecond seeing divided by 3 = 1 arcsecond or in better seeing 2 arc seconds divided by 3 = .66 arc seconds.

So .68 is close to ideal sampling. This means then your camera will produce maximum sensitivity and resolution and that the light is not being spread too thin over the chip or not too broadly.

With a refractor of 115mm or so, typically that will mean about 800-900mm focal length so you will get 1.21 arc seconds per pixel again not too far away from the ideal.

The smaller pixels of the 8300 tend to work better with faster scopes.

Now as far as which 8300 chipped camera to get then here are the considerations:

1. Cost.
2. Performance (they are not all the same by a long ways)
3. Accessories available
4. Autoguiding solutions available.

1. is obvious but there are some hidden costs. Say the SBIG ST8300, very reasonably priced and a popular camera. But it needs a filter wheel, filters and an autoguiding solution (no autoguider or dual chip system).

So make sure you factor in the cost of the camera, the cost of a filterwheel (some have filter wheels built in - well really only the QSI)
and autoguiding.

2. Performance:

Not all 8300 chipped cameras have the same performance.
Performance can be broken down into - sensitivity (called QE for quantum efficiency or how efficiently does the chip convert a photon into an electron). You get a bit more QE with no cover slip over the chip. A FLI Microline 8300 or an Apogee U8300 can be specified with no cover slip. This can also reduce annoying small halos around stars.
Without the cover slip a FLI Microline 8300 gives 60% QE which is very high.

Cooling. Cooling reduces noise. Higher cooling then is better than lesser cooling. The best cooling cameras I am aware of are the FLI and the Apogee both slam the 8300 down to -35C easily. The FLI does it very quickly the Apogee very slowly (30 minutes) which some don't like.
ST8300 not sure of but probably 40C below ambient which will give you
-20C most of the time and -25 to -30C in winter. That's quite cool and the chip should be quite clean at that temp.

QSI is the weakest in cooling although I see they have a series 600 with enhanced cooling now to address that weakness.

Next is readout noise. This is the noise the camera generates during the chip reading process. FLI is lowest. Apogee is very low. Not sure where the SBIG is there. It all adds up.

Next would be miscellaneous noise from the electronics. FLI is very clean
(probably the cleanest) Apogee would not be far behind. Now this is where the SBIG probably falls behind. Its not the end of the world as it cleans up with standard processing but it puts more pressure on that being done very well.

3. Accessories:

Filter wheels, compatibility with electronic focusers, ease of getting adapters, adaptive optics unit availability.

QSI are the best here with a combined filterwheel and offaxis guider giving excellent flex free autoguiding so if you have a decent mount you are very likely to get round stars. Which is a large part of the battle with imaging.

So I know FLI, Apogee and know about QSI and ST8300. You would do well with any of these. QSI is probably best bang for your buck as it incorporates the filter wheel and offaixs guider. FLI is the highest quality and highest performing camera. It is the fastest in download time, it has the best cooling, the lowest noise, has a sealed chamber with inert gas so no desiccant and has a no cover slip for the chip option. It is light, extremely well made and rugged. It has excellent jacks for power and USB (the SBIG has very cheap and weak jacks that can fail).

FLI has RBI control. This means residual bulk images or ghost images. That is if you take an image of something bright these chips tend to keep a ghost of that image into the next image. I think Apogee also may have RBI control as well now.

There is also a new Apogee range called Ascent. New and untried but probably quite good and cheaper.

I can't comment on QHY or Atik except that QHY would probably be a lower scale option and would not perform as well as the above. Atik is an up and coming maker as well but both of these guys were small and cheap type cameras now offering more expensive and bigger chips.

Starlight Express is another excellent camera maker and they have a range of options from guiders to adaptive optics. They have really low noise cameras.

Mono versus Colour. Colour is simpler and requires no filter wheel and filters and is therefore cheaper. Results can be great on the brighter objects but dimmer objects starts to show the lack of sensitivity. Typically mono chips are 50% more sensitive - ie 8300 mono is around 60% QE but one shot colour is more like 30-35% QE. A big drop. You'll see a lot of extra noise in your images especially in the dim areas.

But its a good way to start off with CCD imaging. And its cheaper and every shot counts (you need luminance, red, green and blue filtered images with mono cameras to get a colour shot).

Also mono means you can do narrowband imaging more easily - Halpha and others. One shot colour can do them but not that easily and you lose a lot of performance in that area and they are not really suitable for that unless again its a really bright object.

So QSI is probably the least expensive and most integrated package in the 8300 range as it has an internal filter wheel, and an offaxis guider and if you get the later souped up cooling version decent cooling as well.

That would be my pick.

http://www.optcorp.com/ProductList.a...-320-1232-1876

If you want absolute best then its FLI. Best cooling, highest QE, RBI control, fastest downloads, lowest noise. lots of accessories, no cover slip option.

Next is Apogee (similar to FLI but the slow cooling whilst it doesn't sound like much is very irritating and inconvenient perhaps their new Ascent camera does not do that) and Starlight Express. But these all need filter wheels and autoguiders and off axis guider or a guide scope (not recommended especially for the RC8 you will have hell trying to get round stars).

The 4020 chip is also an excellent chip for imaging you should consider.

One other point about CCD cameras that is worth mentioning.

Most of the modern cameras have their firmware on an internal flash memory. The SBI STX does but the ST series and STL series does not. I think Starlight express does as well and not sure about Atik or QHY.

What that means is the drivers are loaded into the camera from the computer and it takes a little while to do that. If the power gets interrupted (which happens very often with my ST402 as it has a cheap and weak power jack - this reminds me I need to replace that jack) then
you will get an error message when you go to take an image.

Reconnecting the power will not reconnect it in the software. You have to close down CCDsoft and reopen after you have repowered the camera. Wait the 25 seconds or so for it to load the drivers and then reconnect. This means losing your cooling etc. and autoguiding and restarting everything. OK, if everything is working well it probably would not happen that often but it is surprising how often it can still occur.

Modern cameras have the drivers in the camera. My Apogee and FLI cameras and Starlight Express cameras connect instantly. The SBIG takes about 20 odd seconds and sometimes fails. The others almost never. Also you can unplug the Apogee and FLI camera and plug it back into the computer and it is still running at the same temperature and ready to go. NICE. Especially at 3am when you are tired and cold. A lot less swearing!

The other consideration is download times. Slow download times mean the autoguider stops when the download is in progress and the tracking errors build up. If you started another exposure straight away you would be starting at maximum guide errors which then reduce over the first 20-30 seconds of the image. So you have to program in a delay before the next imag starts. FLI was fastest with 1 second downloads with a 1x1 binned image - lightning. Apogee wasn't too bad. I see QSI series 600 has the same download speeds now as FLI - excellent. Also they have -45C ambient cooldown. Plus with the fast downloads, the drivers on board, the off axis guiders, the internal filter wheel means I think they have now overtaken FLI in practicality. FLI have some other nice features not sure QSI matches like antireflection coatings on quartz CCD windows, sealed chambers with inert gas that do not need desiccants etc and the option of no cover slip which gains a bit of extra QE and less halos.

The only thing they haven't gotten now is ghost image control. That is called RBI (residual bulk image). That means if you shoot flats at dusk then the chip will retain some of the charge in the deep layers of the silicone. It slowly leaks out during the later exposures meaning your darks will not match the lights 100%. All full frame KAF series chips do this. Some worse than others. The 09000 chip I believe is the worst. Without RBI control you would have great diffifculty in using a 09000 chip.

I have used several KAF chips and I can't say that this has affected my images or if it has I am unaware of its effects. My FLI camera has the ability to handle this by an infrared flash of the sensor before it takes a light. You take your darks also preflashed in IR and you can control how much it is preflashed. Now your darks and lights are matched more exactly. Richard Crisp has written a paper about this with examples and he is a leading exponent of this technology. Apogee also have RBI control. I don't think any of the others do. Again I am not sure how much difference you would see in your images from this effect. I should try it out to see for myself if it is worth the trouble.

Another aspect of course is weight. Lighter is better. FLI Microline is light, Apogee Alta is medium to heavy, Apogee Ascent would be light, Starlight Express would be light, SBIG 8300 light, SBIG STL medium.

As far as QHY and Atik goes I know nothing so I can't comment.
They are up and coming makers. I had a little Atik camera once which was a cheap ToUcam type camera so they have come a long way.
There is another new maker called Morovian. Again, I know nothing about them. But the above and preceding principles still apply."
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Old 17-06-2012, 08:43 PM
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Also note that since Greg compiled that great info, SBIG released 2 new versions of the 8300 based cameras.

The STF and the STT. Both have better cooling and better integrated systems than all current KAF8300 range of cameras. They also cleaned up read noise. The packages they are doing on Camera, Filter wheel and OAG8300 are very good.
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Old 17-06-2012, 08:49 PM
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jjjnettie (Jeanette)
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You wouldn't be interested in testing the water first with a smaller set up?
A nice wide field ED80 will still deliver the goods and it's much easier to guide at that focal length.
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Old 17-06-2012, 09:57 PM
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Yes, plan to be kissing 30-40% of your investment bye-bye if you find this is all too hard and not for you. You can learn an aweful lot with a simpler less intimidating and less expensive investment and still have lots of fun.

Expert = someone who has made all the mistakes that can be made in a small well defined field.....
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Old 18-06-2012, 11:08 AM
rthorntn (Richard)
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A big thank you to everybody.

I think I will buy a second hand Meade ACF and an EQ6, this is probably not ideal for astro but it is very versatile?

I already have a Canon 50d so I will try that out first. My main concern is light pollution being harder to deal with with on an SLR?

The mono CCD looks like a good idea because ultimately if I couldn't get acceptable results I could focus on narrowband. I will be using the scope in my backyard which is like 7k north of Sydney CBD (another concern is I can't see the horizon from there).

Thanks again.

Cheers
Richard
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Old 18-06-2012, 06:13 PM
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It's very true the NB filters on a mono CCD may well give you the best signal through the skyglow Richard, but if you haven't learned the ropes with aligning, tracking and guiding you still won't get a good final result. You really don't want to be taking pics above 1m focal length if you can help it (and F10 focal ratio makes collecting good data a time consuming affair). A reducer on an SCT might get you down into a more manageable guiding ballpark and also drop the F ratio. Flexure or off-axis guider issues can be more "exciting" the longer your FL.

I'm not an SCT guy however - others here with plenty of experience may comment.
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Old 18-06-2012, 07:05 PM
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cometcatcher (Kevin)
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Quote:
Originally Posted by rthorntn View Post
I already have a Canon 50d so I will try that out first. My main concern is light pollution being harder to deal with with on an SLR?
Photographing with a deep sky / light pollution / nebula filter in the optical path should help a lot. It's not narrow narrow band, and you still get colour as they pass Ha and O3 although it's a little shifted. I'm getting good results with this combo but using fast F ratios because the filters do reduce the total brightness significantly.

I reckon you would get reasonable results with a good ED refractor and a wide band filter in LP skies.
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Old 18-06-2012, 07:24 PM
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Personaly I dont beleieve in light pollution filters. They impact your star colors and signal especially on some DSO's.

You are better off havign good full well depth and exposing longer , thne use processing to remove the skyglow and any gradients.

Its hard enough getting good signal without adding the need to have even more frames to compensate for a light pollution filter.

Just personal preference, but also based on experience with fainter objects from Bortle 6 skies.

I guess if you are in even brighter skies than bortle 6 then LPT may be neccessary , but at that poitn you may be limited to narrowband filters anyway.

Agree with other comments here. I would not suggest any kind of SCT for a beginner who wants to learn astrophotography. Buy a 2nd had ED80 or similar plus the EQ 6. learn the ropes on this, then go longer focal length if you want to.
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Old 18-06-2012, 07:46 PM
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It's just that we've seen people crash and burn so many many times on this forum.
It's not just a matter of slotting the camera in and away you go.

For a scope of that focal length, prepare to spend the first hour and a half of your night in just setting up and aligning before even thinking of taking your first photo.
With my ED80, Heq5Pro, I can be set up, drift aligned, framed, focussed and imaging in 3/4 of an hour, on a good night, if nothing decides to play up.
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Old 18-06-2012, 07:49 PM
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Have you thought of going along to your local astro societies open night?
You'll get a first hand look at a variety of scopes and set ups.
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Old 18-06-2012, 08:34 PM
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And if there are more than 3 imagers present on the field, listen for the mumbling and swearing that inevitably happens on and off all night long
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Old 19-06-2012, 06:40 AM
Poita (Peter)
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Quote:
Originally Posted by jjjnettie View Post
It's just that we've seen people crash and burn so many many times on this forum.
It's not just a matter of slotting the camera in and away you go.

For a scope of that focal length, prepare to spend the first hour and a half of your night in just setting up and aligning before even thinking of taking your first photo.
With my ED80, Heq5Pro, I can be set up, drift aligned, framed, focussed and imaging in 3/4 of an hour, on a good night, if nothing decides to play up.
If out in the field, I would agree, but if in a suburban backyard you can leave the EQ6 setup and aligned and permanently under a cover, then setup and alignment takes less than half an hour and you are on your way.

With alignmaster and the new EQ6 firmware I can setup at a dark site with an EQ6 and C9.25 and be imaging within 45 minutes of parking the car.
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Old 19-06-2012, 09:58 AM
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If out in the field, I would agree, but if in a suburban backyard you can leave the EQ6 setup and aligned and permanently under a cover, then setup and alignment takes less than half an hour and you are on your way.

With alignmaster and the new EQ6 firmware I can setup at a dark site with an EQ6 and C9.25 and be imaging within 45 minutes of parking the car.
If I'm having a run of clear weather, like now, I'll leave the scope and mount set up too.
If only I could do that all the time. sigh....
Not having a fence around the yard, my gear is in full view to anyone who passes by. So if I have to go into the big smoke, the whole lot has to come back inside again.
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