Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

Which scope/mount for imaging?

FLO

Recommended Posts

MartinB

MartinB

Posted
Posted

Ah Jamie you killjoy!! A budget is just a starting point for negociation isn't it? Anyway, if you are going to spend a lot of time on a target goto isn't that vital

This thread's going to run!

periodic error is as you say Steve. Mounts vary in their ability to correct it but don't really know anything about that.

Light pollution can be well dealt with using filters although a CLS will turn your colour images a funny colour - anti orange! That can be sorted with processing as you know. For emission nebulae narrow band filters are the absolute business and enable imaging of dim objects with any sort of light pollution but they aren't really compatable with colour chips or DSLRs

Lots of brilliant results with DSLRs - see James and others

That is a big scope even for an EQ6 and an additional problem with newts is lack of focus travel. Dont know how well they work with DSLRs. Remember the mount is far more critical when imaging than for visual work.

Most deep sky work is low mag and resolution isn't an issue. Light capture is but the modern technique of stacking works wonders in this regard. Aperture is still an issue but nothing like as significant as it is for visual. Some of the finest images are taken using short focal length fracs. I am sure you will get much better results with one of those than a large newtonian.

Link to comment
Share on other sites
  • Replies 64
  • Created
  • Last Reply
MartinB

MartinB

Posted
Posted

How is that info stored and then fed back to the drives Gaz. I know my NS8 can store the info and it is possible to use computer software as well. Can you do it on any mount with a guide port?

Link to comment
Share on other sites
FLO

FLO

Posted
  • Author
Posted

Some of the finest images are taken using short focal length fracs. I am sure you will get much better results with one of those than a large Newtonian

I take your point but are 'affordable' APOs, with two-element objectives, suitable for use with the larger imaging chips like those in DSLRs?

Link to comment
Share on other sites
Jamie

Jamie

Posted
Posted

Dunno about other mounts Martin but the Losmandy has a thing called PEC

Periodic Error Correction

No software needed just flick a switch and yer off and running takes about ten minutes to

set it up.

Link to comment
Share on other sites
GazOC

GazOC

Posted
Posted

How is that info stored and then fed back to the drives Gaz. I know my NS8 can store the info and it is possible to use computer software as well. Can you do it on any mount with a guide port?

Its usually kept in the mount but is lost when you switch the mount off but you can download your PEC results to a laptop and feed them back into the mount next time you setup to save time. Most (all?) mounts with a guide port have PEC.

Link to comment
Share on other sites
FLO

FLO

Posted
  • Author
Posted

I take your point but are 'affordable' APOs, with two-element objectives, suitable for use with the larger imaging chips like those in DSLRs?

Absolutely

More specifically, aspherics aside (something astro scope manufacturers have yet to embrace), can it provide a flat-field?

Perhaps it doesn't matter.... ?

Link to comment
Share on other sites
GordonCopestake

GordonCopestake

Posted
Posted

You can buy field flatteners but to be honest unless you are getting into imaging in a big way you dont need all that paraphanialla. Do you already have a GEM mount? If so you can probably start imaging with what you already have and then see where to go from there. Saves you some pennies too.

Link to comment
Share on other sites
russ

russ

Posted
Posted
I take your point but are 'affordable' APOs, with two-element objectives, suitable for use with the larger imaging chips like those in DSLRs?

ED80 is a superb imaging tool, and in the real world with live, it's the best you'll get on your budget. Only slight downside when using a large CCD such as a DSLR is the field is not quite flat to the outer edges. But you have to look real hard to see it.

False colour etc is non-existent in the ED80.

As for a Losmandy mount.......pure pipe dream I would say. I've only seen two for sale in the last year. One would have left you with £5 for scope and accessories. The other was more reasonble but was snapped up in nano seconds. Steve, you would need to be searching the ad sites night & day for perhaps years waiting for a GM8. And even then you would need the reaction time of a Mongoose to snap up the deal.

Back in the real world....I still say a Skywatcher HEQ5 or Vixen GPDX. And the ED80 is the perfect scope to start out imaging with. Short focal length, widefield, takes a focal reducer. Unguided images upto 2mins. DSLR is certainly easy but Martin's images look superb with the Atik. It's just the flaff of using a laptop and all the cables too.

Speaking of cables. The HEQ5 and EQ6 are ultra streamlined. No mass of cables everywhere like the GP, LXD, CG5 or Losmandy. No cord wraps. One power cord and one controller cord.

As Martin says, this thread could run and run. Everyone has a personal take.

Russ

Link to comment
Share on other sites
GazOC

GazOC

Posted
Posted

I appreciate the strenghs of a short-tube APO but I still, currently, favour a large/fast scope for it shorter exposure times and greater resolution; shorter exposures = less noise and less star-trails from tracking inaccuracies ..... I think?

The apo will still be easier to "learn" on and more forgiving because of the shorter focal length.

Link to comment
Share on other sites
MartinB

MartinB

Posted
Posted

What a great thread Steve! Rus is spot on as always. Gordon has a good point with the Eq3. As Gaz says go for a short focal length apo rather than a big newt. I know the newt is fast not the finely honed imaging instrument that the apo is

Link to comment
Share on other sites
Kaptain Klevtsov

Kaptain Klevtsov

Posted
Posted

Probably (I already have a camera) :|

Here's the first of many questions:

In photography, an f4 lens is an f4 lens. Is this also the case when astro-imaging? For example, other than a theoretical increase in resolution, is their a benefit to having a 10" f4 scope over an 8" f4?

AhHaa!

The 10" f/4 'scope has a focal length of 40" whilst the 8" only has a focal length of 32".

Scopes work the other way to camera lenses so your 400mm f/8 lens would translate to a 50mm (2") f/8 'scope.

The f/ ratio is the ratio of diameter to focal length, so the 10" f/4 gets the focal length from the aperture (front hole size) X f/ number i.e. 10" X 4 = 40".

The zoom-inedness of the image depends on the focal length as with camera lenses, but with 'scopes you have to work this out.

I think that 'scopes use the aperture for the description as this is fixed. The focal length is something that can be messed with using a Barlow lens (=teleconverter) or a focal reducer (=backwards way round teleconverter).

WRT exposure times, these are based on f/ numbers and for the same exposure time of a target with a 10" f/5 'scope or a 4" f/5 'scope the image captured would have the same brightness on the screen. However, the 10" 'scope would get you much closer in than the 4" with a much smaller field of view or higher magnification.

You can use a Barlow lens to double (typically) the focal length of a small 'scope to give you the same magnification as the bigger one, but the f/ number doubles, then you need four times the shutter open time with consequent boredom and the mount errors get horrendous.

There is no mount / 'scope combo suitable for imaging, they all don't work for everything that they're not good at.

Might I suggest that you look at the images posted and see what floats your boat as the necessay 'scope is dictated more by the target than anything else.

I have built a great big 12" f/5.6 thing which couldn't get a nice image of the veil nebula even if I was 10 times as good as I am, as it cannot do the field of view. My little tiny 80mm f/5 'scope (this is really a manual 400mm f/5 telephoto lens rebadged) can easily do the wide angle (comparatively speaking) views necessary there. The skelescope is just the job though, for much smaller objects like M51, M101 and the ilk.

WRT the mount, I used a HEQ5 with very good results until I got aperture fever (biggunitis) and had to get the EQ6 as the 'scope got too big. I can totally recommend the HEQ5 (mine's got goto as well, which is nice) and I would recommend a short focal length big aperture 'scope to get the exposure times down as low as possible to help with PEC issues, alignment problems as well as getting faster results followed by better images because of the larger number of sub-exposures that you can do in an hour.

HTH

Captain Chaos

Link to comment
Share on other sites
OXO

OXO

Posted
Posted
Steve, I think your idea of starting off with some wide fields using camera lenses makes a lot of sense.

I'll second that :D

Steve how is your polar alignment skill's? if naff Pratice Pratice PRATICE because at the end of the day if you can do good Polar Alignment pretty much whichever setup you go for will work for you :D

Link to comment
Share on other sites
FLO

FLO

Posted
  • Author
Posted

how is your polar alignment skill's?

Can't say,

Near enough has been good enough for regular observing.

No doubt I shall have to be more precise; is there much difference (ease of use and quality) between the polar-scopes supplied with the HEQ5/EQ6 and the Vixen Polar scopes?

I have seen Greg lining up his HEQ5 and it seems straight-forward enough...

Link to comment
Share on other sites
OXO

OXO

Posted
Posted
No doubt I shall have to be more precise; is there much difference (ease of use and quality) between the polar-scopes supplied with the HEQ5/EQ6 and the Vixen Polar scopes?

The slightest off set on your Alignment can mean Min's of exposure gone to trailing stars Steve,the EQ6 Polar alignment scope is illuminated which is nice and makes life much easier, my Heq5 did'nt have this feature, cant speak for the Vixen ones though having never owned one.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.