GSO CF RC8 or Skywatcher CF f4 Newt

[Crushellon]

Cant decide which scope to go for. Other than different focal lengths and speeds has anyone got any opinions on these two scopes ie: build quality and ease of installing a heater on the secondary. There's an rc8 on the forums at the moment with a moonlite focuser for $1200...

[alocky]

The main factors will be the type of camera you intend to use and the image scale you are hoping for. The newt will need a coma corrector for imaging at f4, but for the same image scale you can use a smaller sensor and much cheaper filters to get fairly similar results. For the cost of an rc8 you can probably get a larger fast newt, too... For visual, the newt would probably be better, although there's not likely to be much in it.
Cheers,
Andrew.

[glend]

Go with the Newt. I had a GSO RC08 and it drove me crazy; you need to have extreme patience with them but they can produce great results. They do not come supplied with focuser collimation rings and these are necessary for focuser alignment. Sure you can stick a Moonlight on it, but without the focuser collimation ring (an extra $100) you would be messing up the rotation ability of the Moonlight if you tried to adjust it in a fixed position to the secondary centre spot. Most people wind up buying extra collimation aids for the RC like the Tak Collimation scope (add another $230 or so for that), or a Howie Glatter Concentric Ring laser.
Newts, for most people are much easier to live with.
Of course the RC will give you long focal length that the f4 Newt will not. You could consider an f5 newt, and the GSO ones are fine and good imaging scopes, at a wonderful price. On an NEQ6, the GSO 10" f5 Newt might be a tad heavy for imaging depending on your camera imaging train setup.
Get a Baader MPCC MarkIII Coma Corrector, a magic device.

[Crushellon]

I have a baader mpcciii for my current scope and I'm getting an asi1600. One of the main considerations for me is a readily available secondary heater because as I found out with my first trip to a dark site last week I won't get much imaging done without one. I'm pretty comfortable with using/collimating a newt now but I like the image quality and focal length of the rc's.

If I went for the newt it would be the 10" cf f4 from Skywatcher, cause it's light enough for the mount.

[jjjnettie]

I'm pretty sure the RC8 has a secondary heater installed.
I have to take more pics when I go pick it up. :)

[glend]

Ok Tim, just trying to help. Collimating an RC is nothing like collimating a Newt.

[jjjnettie]

The trick is knowing that you only should adjust the secondary. Leave the primary alone!!!!

[Crushellon]

Thanks,I appreciate it. I didn't even know collimating them was a big deal, I have no idea at all about using an RC. I just meant that the fact that I'm comfortable with a reflector is one of the pros for staying with a newt.

[DJT]

Hi Tim

The rc8 with that moonlight is a bargain. Here is also one up from David Naskies which is a steal as well. Check out some of the images he was churning out with it.

What I like about mine is that it has a huge amount of back focus and the moonlight handles the imaging train well ( stl603 and mmoag)

With the as1600 chip you won't see too much of the curvature you get with an RC because of the mirror design as well. I don't use a flattener and just crop away any issues.

collimation is fun but once dialed in you don't need to adjust much, well, when you have a permanent setup that is. Tweaking with the secondary gets you where you need to be, you should very rarely need to adjust the primary Search ICE for Als collimating aide as well. Great for tweaking the secondary.

Focus holds very well during the night.

If you did want to throw a little extra money at the scope, the tak collimater plus adapters makes life easy as does the GSO tilt ring. I don't use laser gadgets

Will be fine on an eq6.

Of course it's slower than the newt but that's just a question what you want to image and then just Patience.

[alocky]

I retrofitted a secondary heater to my 10" newt, and it was very straightforward- but, at 3.8 micron pixels that camera is not a great match for the rc8, and is almost over sampling a 10".
Cheers,
Andrew.

[lazjen]

Binning and/or a reducer would make the scopes match better to the camera, right?

[alocky]

Sure - avoiding binning though because it seems a waste,
At f8 an rc8 with that camera will give 0.49 arc secs/ pixel which is a bit ambitious without adaptive optics (ESO style, not amateur). A 0.8 reducer gives you .61 which is starting to be more realistic especially if you have good seeing, but still a bit optimistic.
A 10" f4 will get .78 "/px which would be perfect.

[lazjen]

I'm not sure if it would work with the RC8, but I can get a 0.67 FR working with my RC10. For the RC8, if it works, you'd get 0.72 arc secs/pixel.

[Crushellon]

So I ended up going with the rc8.... I got a pretty good deal on the rc8 & an ed80 both with moonlites and a moonlite controller, an 0.85x Skywatcher reducer/corrector, heat straps for the whole lot and a dual channel dew controller. Haven't got the camera yet so I'm still open on that one, but really though for a cooled camera at $1600 is it really that bad a match? I have to consider that I will be using it with both rc8 & ed80 now that I have both scopes. (Wasn't really in the market for an ed80, but I couldn't pass up a good deal)

[lazjen]

Have a read of this page (http://astronomy.tools/calculators/ccd_suitability) and use the calculator at the end. Plug in your scope and camera, with / without the reducer and see the results.

If you do that, you'll see that you're probably going to be oversampling with the ASI1600, which is not ideal.

If you had a 0.67 reducer and it worked for focus, etc, then the ASI1600 would be fine.

[Crushellon]

Not really keen on going for a reducer, kind of defeats the purpose of the scope if I'm just gonna bring it back to ~1000mm focal length. So why is binning a bad idea? I figure the camera is a good match for the ed80 at 1x1 and good for the rc8 at 2x2? If I got a camera with bigger pixels Id be under sampling with the ed80 which is really bad as I understand it (which I don't btw:D)

[DJT]

Hi Tim

I found this article useful when trying to get my head around this. There is an excellent diagram showing the relationship between focal length and pixel size.
http://www.skyandtelescope.com/astronomy-resources/astrophotography-tips/of-pixel-size-and-focal-reducers/?c=y

There is an sbig stf8300 in classifieds that might be a better fit for you?

[Crushellon]

I'm going for an osc camera, so the sbig is no good.

[Atmos]

You could always just get another astro modified DSLR. Central DS (http://www.centralds.net/cam/) have quite a nice range of cooled DSLRs. Many of those are likely to have larger pixels that the ASI1600. All depends on budget though I suppose.

[codemonkey]

Sampling at 0.49"/px is going to be pretty tough. Going by the 3x rule of thumb, that means the total of your guiding error, optics and seeing would want to be about 1.5" for you to be appropriately sampled. Not undoable, but you need a good mount and good seeing. Even with a reducer bringing it down to 0.61"/px it's not going to be easy. Either you need low expectations, or a seriously good mount and good skies.

I also would not bin the ASI 1600. It drops back to 10 bit mode and according to the manufacturer, the only real benefit you get to binning the 1600 is reducing the file size.

If you dither and use drizzle integration, you can "get back" some of that lost resolution on one of those rare nights that everything falls into place and you end up undersampled.

[Crushellon]

I was hoping to spend $1600 on a camera, I could push it up to $2000 if I had to. Needs to be a compromise of being good for both scopes but leaning towards better performance for the rc8 over the ed80(will be running the ed80 with the sw 0.85 reducer/corrector) as the rc8 will generally be the main scope.

[Crushellon]

http://www.bintel.com.au/Astrophotography/Atik-CCD-Cameras/Atik-383L--Colour/1671/productview.aspx

Looks pretty good? $1k over budget new but if I found a second hand one... With 5.4 pixel size it would be OK for both the rc8 and ed80?

[codemonkey]

Probably a reasonable compromise. Those are very different focal lengths so you're not going to get one camera that's perfect for both.

It'll still be tough on the RC8, but it's likely to be a bit undersampled on the ED80. You could use the RC8 on the good nights, the ED80 on the bad nights, and maybe drizzle the ED80 on a typical night.

Someone has a mono SBIG 8300 (that Atik 383 you linked to is the colour version of the sensor) for $1600 at the moment. With the extra money you could put it towards a filter wheel and some filters and end up with a better rig.

http://www.iceinspace.com.au/forum/showthread.php?t=146551

[Crushellon]

I'm a married father with 3 children under 4... Mono is out of the question for me, especially because my setup gets set up and packed up every night. It has to be OSC... As much as I would like the optimal results that I would get with mono+filters I just don't have the time. Maybe in 5 years when I have an observatory in the backyard :lol:

[codemonkey]

With an automated filter wheel it won't make a difference to overall time. In fact, you'll get better results in the same amount of time. That said, it does require more effort in post processing, and maybe you're not prepared to do that. Fair enough, just a thought!

[Crushellon]

Spending prolonged periods doing post work is fine... I can point from my computer chair :rofl: however I was under the impression that it takes 2+ nights with impeccable guiding for super long subs to get anything to work with doing mono/filter work? Which would mean setup/packup/staying up to monitor the weather for multiple nights. Don't get me wrong, the kind of results that you get with said type of setup is exactly what I'm after long term. But I don't think I could pull off the multiple nights working to get anything worth working on at this point with kids to look after.

[Atmos]

In that respect OSC and mono are exactly the same, the amount of integration time needed that is. For instance:

20x180s with an OSC is a total of 1hours exposure.
5x180s LRGB is the same integration time but will be of higher quality. It will have a higher resolution due to not having a bayer matrix and you can capture straight luminance for detail and brightness.

There is no guiding difference nor any single sub length difference between mono and OSC. This is largely determined by your sky brightness (moon and light pollution), the focal ratio, pixel size and camera read noise.

NGC 6822 from my last imaging run (http://www.astrobin.com/full/258077/B/) a couple of weeks ago. This is less than two hours worth of data and the vast majority of that is just luminance (tossed out most of my colour data and half of my luminance). It could certainly do with a LOT more data but so would a OSC camera at 1.8 hours :P

One of the benefits of a OSC is that you don't have to worry about how many of each filter you get. I cannot comment too much on OSC imaging as I have done VERY little of it, I jumped straight into the deep end, was a struggle at times but I haven't regretted it.

[Crushellon]

Orly? Intriguing. So say I did get a mono camera... Can I just use it without any filters for black and white photography while I save up for filters/filterwheel?

[lazjen]

These might do to start with for filters/filterwheel:

http://www.bintel.com.au/Astrophotography/Filters/ZWO-LRGB-Imaging-Filters--1-25--/2035/productview.aspx $149
http://www.bintel.com.au/Astrophotography/Filters/ZWO-Filter-Wheel--1-25--/2033/productview.aspx $149

You'd have something to at least play with to learn the ropes further.

[codemonkey]

For OSC you're trading resolution and the ability to do narrowband for the convenience of capturing RGB data simultaneously. With an automated filter wheel you can get better data (in terms of both SNR and resolution) in the same time.

You can do B&W without filters, but the refractor at least will probably be performing less than is optimal that way, because the camera will capture a very wide range of light, and the refractor can bring only a subset of that range to focus which will make the images less sharp than ideal. The RC8 will be less affected due to the fact that it's got a mirror instead of lenses.

Don't get yourself a manual filter wheel if you need to be as hands off as possible, it's a waste of your money. Save the money and put that towards an automated filter wheel. Could be worth getting some of the cheap LRGB filters to play around with though.

You'll also need some software to control the filter wheel and do your image capture. I'd recommend Sequence Generator Pro. It's pretty simple to use, fairly powerful and much cheaper than the alternatives.

[lazjen]

I have to agree an automated filter wheel would be better, but I think they're a bit of a jump in price from the manual versions.

Also, consider APT for image capture (http://www.ideiki.com/astro/Default.aspx), it's much cheaper than Sequence Generator Pro.

Depending on the gear you get and your computing skills, using ekos/INDI has an even better price point: free.

[Atmos]

And a SBIG 8300C (http://www.iceinspace.com.au/forum/showthread.php?t=148056) just came up too so its up to you :P

[Crushellon]

So you guys have sold me on going mono.. Just as a 8300c came up for sale :rofl: now I just need my old gear to sell so I can buy one :) I don't think my wife would appreciate me spending more money until some of it has gone :lol:

Oh and I already have the pro version of apt so all good for controlling it all. I am also gonna run the trial of maximdl on my next session to see if I can guide any better out of the box

[lazjen]

Have you tried PHD2 for guiding?

[Crushellon]

Yeh I've got an neq6 with belt mod and when I do the drift align with phd2 it's a nice straightish line and calibration is all good but I'm getting pretty average guiding with big spikes. Tried to do a pec with phd2 and ascom but the pec line was just oscillating up and down. So that was no good either.

[Atmos]

Random spikes for me tended to mean that my mount needed a clean (regrease) as they disappeared after that. Unless there is an imperfection in the worm gear which will show itself every 7-8 minutes.

I've never done PE correction but my understanding is that it should go up and down :)

[Crushellon]

Just did a clean out when I installed Te belt mod, results were better but still not quite good enough. Was only getting 50-60% usable subs at 120sec. I thought a pec line was suppose to look like a sine wave?

Edit: mind you the only time I've run it since the belt mod was in the field whilst trying to capture, I'm yet to sit down with it for a night and just play with guiding to get it better.

[Crushellon]

So I ended up getting the stf-8300m off the forums and and a cheap set of Lrgb filters and a manual wheel. Do You need to run an IR filter in front of the color filters when using the ed80? The cheap filters didn't have the IR coating that the more expensive ones mentioned. Also would a cheap CLS CCD filter be better than a cheap luminance filter for working in suburbia?

[Slawomir]

Congratulations Tim- we look forward to seeing your images taken with your new gear :thumbsup:

I would also pick a mono over osc any time :)

As for combining filters- I think experimenting will allow you to optimise your particular setup, but I personally would avoid using two filters at the same time (reflections?). Also, I do not expect there would be a significant difference in data collected through a cheap CLS and a cheap Lum filters.

Having said that, I would hold off and save for a good Lum filter, as it plays a vital role in collecting quality data for the final Tri-colour picture.