Schmidt Newtonian for astrophotography?

[ausastronomer (John Bambury)]

Originally Posted by troypiggo

“Better performing scopes for AP” - of course if budget is no issue. I’d be interested to see your recommendations for the same cost as SN10, since that’s what the OP was asking about.

The Meade SN10 out of the box isn't a very good telescope. The focusers and the mirror cell / mounting sytem leave a lot to be desired. Further, some of them have serious optical issues. I was able to observe Mars in stereo without binoviewers during the August 2003 opposition using long time forum member Tony Hitchcock's (Itchy) Meade SN10. The telescope was unique in that in 45 years of observing it is the only telescope I have ever used that was able to provide stereo images of every bright target it was pointed at. It provided 2 very fuzzy balls of Mars side by side with almost no detail of any description visible.

As one of the earlier posters said, his Meade SN10 has been somewhat modified to the stage where it's now a decent telescope.

An 8" or 10" F4 Newtonian is a whole lot easier and a lot more likely to be a decent performer without a good bit of work and modification.

Cheers
John B

[peter_4059 (Peter)]

Originally Posted by ausastronomer

As one of the earlier posters said, his Meade SN10 has been somewhat modified to the stage where it's now a decent telescope.

An 8" or 10" F4 Newtonian is a whole lot easier and a lot more likely to be a decent performer without a good bit of work and modification.

Cheers
John B

John,

To be fair I think you would find a lot of people purchasing GSO or similar newts would replace the focuser and probably also make other mods to stiffen the area where the focuser attaches. They might also replace the primary colimation springs and flock the inside of the tube. They would also need to purchase a coma corrector. I did all of these things with my GSO newt and have done similar mods to the SN10 so I think it is a bit of a stretch to suggest these newts work well out of the box.

Here's a good thread on the topic from someone that is achieving outstanding results:
http://www.iceinspace.com.au/forum/s...d.php?t=111441


The biggest challenge with the sn10 is getting a suitable coma corrector in my opinion. For me the jury is still out on that and I might be in denial however I'm planning to keep trying as the advantage of being dew free is a big plus based on my years of astrofest experience with the newt.

Peter

[Space Cadet (Greg)]

Thanks for the discussion guys, i am learning lots.
My main issue on a shoestring/dental floss budget is what to initially buy. Although the Mak Newts appear better, then i need a mount, etc, so $$$ are still an issue. i am currently considering 2 options
1. A HEQ5 mount with a ED80, 2"diagonal and 10x focuser and 1 eyepiece for $1600, local area, or
2. A EQ6 mount with f4 10" Schmidt Newt, with 80mm short tube finder with autoguider, plus telrad, motofocus, variety of eyepieces for $2K, with a 30hr road trip

i am happy to do the road trip if it is worth it, but dont want to waste that effort if not. I am also wondering if this option is getting too ambitious?
If either of these options are going to give me a good intro into the game with the potential to then buy better quality glass later that could also work for me.

I am told the EQ6 is a better mount option for the future potential to add a larger scope as my aperture envy develops. Makes sense to me, however there seems to be a myriad of EQ6 and EQ5 options, so my confusion is growing. Some black some white, then H versions N versions, pro versions, ahhh! A nice comparison matrix would be helpful Skywatcher!

Maybe i just need to learn some patience!
More wisdom and opinions please?
Cheers
Greg

[Space Cadet (Greg)]

BTW the Schmidt Newt is a Meade LXD55.
How much should this be worth on its own as an OTA?

Cheers
Greg

[peter_4059 (Peter)]

Greg,

Here's my thoughts:
There have been various versions of the HEQ5 and EQ6 however most of the changes have been cosmetic. There is a newer EQ6 called an AZEQ6 that is different and has some upgrades including belt drives, a larger diameter counterweight shaft and easier adjustment of altitude. It also allows the mount to work in both equatorial and AltAz mode.

There is also a belt mod kit for the HEQ5 and EQ6 and many of the mounts coming up for sale have had this mod done. This reduces some of the errors in the reduction gearing if it is installed well. The belt mod kit comes from Rowan Astronomy in the UK.

http://www.rowanastronomy.com/products.htm

The good thing about these mounts is you can take them apart and adjust their internal workings if you are so inclined. Search/Google "EQ6 Hypertune".

The EQ6 will give you more options than the HEQ5 if you decide you want to use a heavier scope in the future. Many people end up wanting more focal length which usually means a heavier scope. If you overload the mount you will have difficulty getting accurate tracking and end up with stars in your images that look like eggs.

In terms of optics, if you want something easy that you can get good results with on large objects then go for a refractor like an ED80. These are quite forgiving and you will get good results quickly however you will be limited to wide fields of view/large objects. You get what you pay for with refractors and the cheaper ones produce violet halos around bright stars. Ideally go for a reputable triplet to avoid this. You will most likely need to purchase a flattener also -something like this:
https://www.bintel.com.au/product/or...eld-flattener/

Here's a good example of what you might be looking at:
http://www.iceinspace.com.au/forum/s...d.php?t=163203

If you are up for a challenge and like to tinker then go for a Newt or the SN10. This will be a more difficult scope to achieve good results with however it has twice the focal length of a typical 80mm refractor and 10x the light gathering due to the difference in aperture. This reduces the time you need to spend exposing the image. Because it has mirrors rather than lenses you don't get the violet halos - even in low cost ones.

The LXD55 is what I have. For astrophotography the minimum you will need to do is replace the original plastic focuser which is definitely not up for the task. I replaced mine with a motorised Moonlite focuser. For either the newt or the SN10 you will also need a coma corrector - something like this:
https://www.bintel.com.au/product/ba...-mkiii-2-inch/

I believe you would expect to pay $800-1000 for an LXD55 in good condition. These are quite hard to come by and the one I found was in good condition so I was prepared to pay the top end of that range for it.

No matter what you go for, if you are on a shoestring budget you will be making a compromise and will want something better as you progress (that's the path I've been on). The trick is to minimise regret spend so you can upgrade over time without having to offload too many things hence the reason I suggest the bigger mount.

Hope that helps,

Peter

[Space Cadet (Greg)]

Thank you Peter
That does help

[clive milne]

The MPCC is a really bad idea.
For one, it will over-correct the coma, leaving you with as much negative coma as you originally had positive coma.

Not only will it do nothing to sharpen up the outer field, it will destroy the centre of the field as well from the spherical aberration it adds.

Even as a Newtonian corrector, it is a poor choice.

https://www.cloudynights.com/topic/5...or-compariosn/

A simple field flattener would be better.

best
~c

[peter_4059 (Peter)]

I have the MPCC type 1 and 3 and the paracorr. I'm tempted to get a GPU and do a comparison for myself.

[peter_4059 (Peter)]

Originally Posted by clive milne

A simple field flattener would be better.

Clive,

I should have asked, can you recommend a simple field flattener that would work well? I'd be keen to try that option also.

You might find this interesting ...

https://optcorp.com/products/ba-mpcc...-mpcc-mark-iii