dark site blessed beginner

muletopia (Chris) · #1 08-04-2014, 11:22 PM

Folks ,
Another beginner asking about equipment.
I live 30 km from the nearest street light and 5 km from nearest neighbour and 150 km inland. So far so good. Less good is the dust at harvest or dry season seeding time.

Because of the dust a closed tube seems to be the go. My aim, eventually, is astophotography. So I am considering the 7 inch Skywatcher Maksutov Cassergrain.

Does this seem reasonable?

astro744 · #2 09-04-2014, 08:40 AM

Welcome!

The telescope you suggest has a focal ratio of f11.8; this is considered slow photographically. However if your interest is photographing planets then it is fine.

I see this telescope can be bought for about $850.00 with EQ3-2 mount (RA/DEC motors extra). For the same amount of money you could buy a 12"/f5 Dobsonian which would provide over 5.5x the brightness in images, better resolution and give you access to countless objects visually that the 127mm would not even begin to show. However a Dob mount is not suitable for astrophotography although there are variations that offer such capability at extra cost.

You can also add an equatorial (Poncet) platform to any standard Dob mount later. See http://www.equatorialplatforms.com/ This also gives tracking ability for visual observing as well as photography. Another (much more expensive) option is ServoCAT. See http://www.stellarcat.com/

Under dark skies I would go with the largest optics I could afford and know that I can add either an EQ platform or ServoCAT later or get a second photographic telescope with its own mount such as ED80 refractor on an EQ5 (maybe EQ6) mount. This is a very capable and stable photographic system.

Note with astrophotography it is the mount that is more important and the more stable it is the better.

It really depends on where your interests lay and if you're set on photography then go down that path and perhaps others here can chime in with more suggestions on suitable telescopes for astrophotography. If you like what you see visually then buy the biggest optics you can afford as the images will be brighter for the same magnification. I suggest you try and go to any local astronomy club observing night or star party to see what you may like more.

Whatever you get, enjoy!

Pinwheel (Doug) · #3 09-04-2014, 10:47 AM

Quote:

Originally Posted by muletopia

Folks ,
Another beginner asking about equipment.
I live 30 km from the nearest street light and 5 km from nearest neighbour and 150 km inland. So far so good. Less good is the dust at harvest or dry season seeding time. Because of the dust a closed tube seems to be the go.

Welcome to IIS

, Sounds like your near me..lol where about's are you?

raymo · #4 09-04-2014, 12:48 PM

Just a nitpick and a couple of thoughts. The 7 inck Mak is 180mm, not
127mm. Firstly, the Mak gives great images without suffering the coma
that fast Newts do. Secondly, a reducer can be used to make it much faster for imaging. Thirdly, even with a decent stable EQ mount it would be much more easily portable. I'm not knocking large Dobs[I have one myself] ,just trying to balance the info you are getting. Further along you could perhaps get a Dob as well, being as they are so cheap for their size.
raymo

astro744 · #5 09-04-2014, 01:00 PM

Quote:

Originally Posted by raymo

Just a nitpick and a couple of thoughts. The 7 inck Mak is 180mm, not
127mm. Firstly, the Mak gives great images without suffering the coma
that fast Newts do. Secondly, a reducer can be used to make it much faster for imaging. Thirdly, even with a decent stable EQ mount it would be much more easily portable. I'm not knocking large Dobs[I have one myself] ,just trying to balance the info you are getting. Further along you could perhaps get a Dob as well, being as they are so cheap for their size.
raymo

Sorry. My mistake. I had the 127mm in my head for some reason. Yes 7" is the 180mm/f15 Mak. Same comment as before about focal ratio i.e. photographically slow but can be improved with focal reducer.

Disregard previous comments about cost as this one is worth a lot more. However you could buy a 10" to 12" GOTO DOB for a similar cost. Just a thought. Note too Mak's are factory collimated and provided this is good will be OK otherwise they do not readily allow for user collimation. (Depends on the design of the Mak).

Steffen · #6 09-04-2014, 01:19 PM

Quote:

Originally Posted by astro744

Note too Mak's are factory collimated and provided this is good will be OK otherwise they do not readily allow for user collimation. (Depends on the design of the Mak).

Sorry, but I'm puzzled by this statement.

Cheers
Steffen.

astro744 · #7 09-04-2014, 01:46 PM

Quote:

Originally Posted by Steffen

Sorry, but I'm puzzled by this statement.

Cheers
Steffen.

Not all Maksutov-Cassegrain designs are the same as the secondary could be an illuminated spot on the back of the meniscus or a separate mirror that may or may not have collimation screws. Special (factory) equipment or techniques may be needed to collimate the optics if they should ever require it and this may only be if heavily bumped.

Steffen · #8 09-04-2014, 02:20 PM

All MCTs I've yet seen (except for some small Meades with ETX-style integrated backs) had easily accessible primary mirror collimation screws, the Rumak type designs of course also have secondaries that can be collimated.

Collimating a Mak is very straightforward, all you need is a steady night and a mag 1 (or so) star. This can turn out to be a big ask because for precise collimation you need a steady star image at well over 200x. An artificial star is an alternative for people who rarely get good seeing.

However, given that, collimating an MCT is a doddle.

Are you sure you don't have Ritchey–Chrétien or Dall-Kirkham scopes in mind?

Cheers
Steffen.

astro744 · #9 09-04-2014, 02:34 PM

Quote:

Originally Posted by Steffen

(except for some small Meades with ETX-style integrated backs)

Say no more!

Kunama · #10 09-04-2014, 02:37 PM

Quote:

Originally Posted by muletopia

Folks ,
Another beginner asking about equipment.
I live 30 km from the nearest street light and 5 km from nearest neighbour and 150 km inland. So far so good. Less good is the dust at harvest or dry season seeding time.

Because of the dust a closed tube seems to be the go. My aim, eventually, is astophotography. So I am considering the 7 inch Skywatcher Maksutov Cassergrain.

Does this seem reasonable?

If the conditions really are as dusty as that I would think a closed tube would be a very good option, I would hate to start extracting loads of dust out of a opentube 12" Newtonian be it in a Dob cradle or not.

Steffen · #11 09-04-2014, 02:47 PM

Maybe a Mak-Newt then?

Cheers
Steffen.

AstralTraveller (David) · #12 09-04-2014, 03:21 PM

How long is the dust around? If it's not too long it may not be a real issue. Also remember that newts are pretty easy to clean, users do it all the time, and open tube designs can often be cleaned without removing the mirror. Of course the dust will also affect your seeing so perhaps you won't even have the scope out during the dust season.

muletopia (Chris) · #13 10-04-2014, 07:31 PM

No, wheat belt Western Australia is a log way from the Wimmera

Pinwheel (Doug) · #14 11-04-2014, 12:36 PM

Quote:

Originally Posted by muletopia

No, wheat belt Western Australia is a log way from the Wimmera

Maybe update your profile data, Australia as stated doesn't help anyone.

Renato1 (Renato) · #15 11-04-2014, 08:58 PM

If I were you, living in dark sky heaven, I'd go for aperture. As you want to do photography then - if it was going to be a big thing for you - my suggestion would be an SCT, either 8, 9.25, 10 or 11".

Alternatively, get your Mak. It won't be long before you get a big dob - even if you only use it after showers or rain that clean up the dust in the air.

Regards,
Renato

muletopia (Chris) · #16 14-04-2014, 08:40 PM

Folks,
Thanks for the replies, I have to change tack, to 180 mm Mak Cas is just not available,

So any thoughts on the Celestron CGem 800 ?