Buying a new OTA HELP! - Page 2

04Stefan07 (Stefan) · #21 10-01-2016, 04:03 PM

An SCT would be nice but they are just a tad too expensive.

I thought the exact same thing. I want to do so much but I think I do need to compromise with something.

Definitely want both the visual and imaging. I used to have a 127 SLT which was a fantastic little OTA until I dropped it and disconnected the mirrors inside it

I already have a DSLR and used to have a NexImage 5 which I just recently sold so if I can get my hands on a ZWO camera I might just use that as my camera.

Quote:

Originally Posted by DarkArts

Within the weight limits of an HEQ5/AZ-EQ5-GT, your choices are limited.

You want visual and DSO photography and planetary and to guide with a finderguider all on an HEQ5-class mount. That's tough. I think you'll have to compromise on something. My pick would be an 8-inch SCT. The SCT is an all-rounder. You might just be able to guide it (when you have a, say, 0.63 focal reducer fitted) with a finderguider, but I'd go for a camera with big pixels or binning or a better guide method.

You ought to be able to find a Celestron C8 second hand but it might be a tad over $500 ...e.g., 'casstony' recently sold a C8 OTA for under $800.

Here are a couple of packages including C8s (you might be able to convince the seller to split the package):
http://www.iceinspace.com.au/forum/s...d.php?t=141549
http://www.iceinspace.com.au/forum/s...d.php?t=141525

Or, if you're really, really strict about the budget, here's an ad for a C6, which will be well within your weight limit and easier to guide:
http://www.iceinspace.com.au/forum/s...d.php?t=140957

Hope that helps.

Tropo-Bob (Bob) · #22 10-01-2016, 04:51 PM

Quote:

Originally Posted by raymo

The HEQ5 easily carries the 8" f/5 with all it's accessories Bob.
If you look around this forum and elsewhere, I think you'll find that this scope/mount combo is arguably the most popular budget level rig.
raymo

I am a little surprised, but trust your opinion. I briefly had an 8' F5 (with an oversized secondary) and it certainly strained the EQ5 mount that I put it on. My main problem with it though was I thought it was very ordinary for visual observing. Do U find yours satisfactory for visual, and is it also with an oversized secondary? A follow up question if I may to the astro-imagers, are the reflectors with the traditional sized secondary satisfactory (or far inferior) for imaging compared to the scopes with the oversized secondary mirrors?

raymo · #23 10-01-2016, 06:27 PM

Firstly Bob, were you talking about an EQ5 or an HEQ5? The HEQ5 has
a max payload about 40% more than the EQ5.
I bought the 8" OTA used, so have no idea whether it has an oversized
secondary. I may be wrong, but I think the f/5 was made with either vis or imaging in mind, but the f/4 was made primarily for imaging. Someone
else can probably answer your question better than me.
My f/5 is fine for vis, as good optically as my 10" f4.7 Dob.
Sorry for the slight diversion Stefan.
raymo

glend (Glen) · #24 10-01-2016, 06:47 PM

Many of the 8 & 10" newts sold as imaging newts, like the GSO models sold by Andrews have secondaries sized to illuminate a camera sensor thus they are larger than visually optimised newts which only have to illuminate an EP spot and your pupil. They can be used visually by inserting an extension tube in the focuser to move the EP further away in the light cone to achieve focus. Thus these imaging newts are not as good from a contrast point of view when used visually (larger central obstruction). Newts optimised for visual use may exhibit vignetting of image sensors. There are scope like Mak-Newts which are good both visually and imaging wise, running a smaller secondary mounted directly on the corrector - thus no diffraction spikes and undetectable coma. However they are heavier than standard newts and cost more. The Skywatcher MN190 is a great example but can't be used on a HEQ5.
Most scopes are compromises in some way, especially at the budget end of the market.

04Stefan07 (Stefan) · #25 10-01-2016, 07:18 PM

No stress.

Not really any closer to deciding.

barx1963 (Malcolm) · #26 10-01-2016, 07:27 PM

If it was me I would buy the best scope you can afford for what you want to do now. If that is imaging, get the best imaging scope you can, if visual go buy a dob. Attempting to do both is going to involve compromise and leave you unimpressed.

Malcolm

04Stefan07 (Stefan) · #27 10-01-2016, 07:30 PM

Cheers Malcolm.

Yeah compromising can be difficult! I am sure the scopes mentioned below are better suited for imaging but surely they can be used for visual. They may not be a 10/10 for visual but a 7 or 8/10 for visual would be good enough!

Quote:

Originally Posted by barx1963

If it was me I would buy the best scope you can afford for what you want to do now. If that is imaging, get the best imaging scope you can, if visual go buy a dob. Attempting to do both is going to involve compromise and leave you unimpressed.

Malcolm

barx1963 (Malcolm) · #28 10-01-2016, 07:43 PM

In that case an imaging newtonian can always have a simple dob mount built for it fairly cheaply. This avoids the main issue with newtonians on EQ mounts which is the dastardly positions the eyepiece ends up in. Of course as mentioned the imaging newts are fast (f4 or f5) so can be a bit coma affected. That said, I have built a dob using an f4 imaging mirror and it works fine, I just ignore the outer part of the field! The larger secondary means a bit of light loss and lower contrast. the issue then would be will a HEQ5 handle it once you put a guidescope, guidecamera and main camera on it?

Cheers

Malcolm

raymo · #29 10-01-2016, 07:43 PM

My SW 8" f/5 is fine for visual, which is what I used it for before taking up
digital imaging [not very successfully].
raymo

04Stefan07 (Stefan) · #30 10-01-2016, 07:47 PM

Sure.

I know that I would like to avoid adding too much weight to the scope which will restrict me on adding accessories such as a guidescope.

The HEQ5 Pro looks like it can take around 13.5kg so a tube under 8kg would be ideal in my opinion, have some accessories then have a few kilograms left.

04Stefan07 (Stefan) · #31 11-01-2016, 10:03 AM

I have composed a list of some scopes (just using Skywatcher as an example, I know other manufactures rebrand the same scopes).

- Skywatcher Black Diamond 120/1000 Refractor
- Skywatcher Black Diamond 150/750 Reflector
- Skywatcher Black Diamond 127/1500 MAK

Have experienced all 3 different design types.

I got to say my favourite is the MAK as what everyone says aperture is most important!

04Stefan07 (Stefan) · #32 11-01-2016, 04:39 PM

Ok I have been eyeing off the 6" Newtonian. There is a Skywatcher one and heaps of GSO ones.

Anyone got any more tips??

04Stefan07 (Stefan) · #33 11-01-2016, 06:18 PM

Am willing to stretch the budget to $700

raymo · #34 11-01-2016, 06:48 PM

I loved my SW 150 Mak, maybe you could find a used one within
your budget, bit slow for imaging though.
raymo

rmuhlack (Richard) · #35 11-01-2016, 07:08 PM

Stefan - what was it about the RC6 that made you decide it wasn't the scope for you? (i'm just wondering what a 150 Mak Cas would offer that the RC didn't, as they are both slow scopes with long FL). I would think the RC6 would be preferable to a 150 Mak Cas if you wanted a scope for deep sky imaging, however i would expect the Mak Cas would excel at lunar and planetary visual/imaging.

04Stefan07 (Stefan) · #36 11-01-2016, 07:17 PM

The RC6 is more for imaging plus it was very weight heavy at the back, more than the SCT I used to have.

Now that my budget is stretched a bit it should make choosing a bit easier.

Quote:

Originally Posted by rmuhlack

Stefan - what was it about the RC6 that made you decide it wasn't the scope for you? (i'm just wondering what a 150 Mak Cas would offer that the RC didn't, as they are both slow scopes with long FL). I would think the RC6 would be preferable to a 150 Mak Cas if you wanted a scope for deep sky imaging, however i would expect the Mak Cas would excel at lunar and planetary visual/imaging.