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Equipment Discussions >> Reflectors

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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: How Big a Mirror Needed? new [Re: FirstSight]
      #6235494 - 12/05/13 02:09 PM

Quote:

As big a mirror as:
1) You can afford that has a high-quality figure;
2) Will still allow you to observe at all altitudes with your feet still on the ground (depends on f-ratio of mirror);
3) Is within feasible size to transport (both in terms of available vehicle and available muscle power).
4) Is within a price range your wife will knowingly approve you purchasing without initiating divorce proceedings.




My thinking:

No photographer would have just one lens or just one camera. Likewise, amateur astronomers need more than one telescope, more than one eyepiece.

Different situations, different objects, different telescopes... Mirror quality is critical for planetary viewing, not so critical for hunting down tiny faint objects. Some scopes are more portable, more transportable some are less...

As far as the Leo triplet.. I think Glenn's comments are of fundamental importance but the photo in question was not representative of what is possible with a 80mm scope. Here is a photo taken with an 80mm apo.

Leo Triplet ED-80 (Eon)
My experiences:

- Larger apertures are a help when skies are light polluted but aperture cannot overcome the loss of contrast caused by the bright sky, it can only provide greater magnification or a brighter overall image but both the galaxy/nebula and the sky be equally brighter.. A small scope under dark skies will show things that cannot be seen with a large scope from a light polluted backyard.

- Observing skills are probably more important than aperture.. Thomas's drawing of the Leo Triplet, lots of us would not see that through a 6 or 8 inch scope.

Jon


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nosmoke
super member


Reged: 11/06/13

Loc: Calgary, Alberta
Re: How Big a Mirror Needed? new [Re: Jon Isaacs]
      #6235551 - 12/05/13 02:39 PM

Wow, if I could see that thru my future scope, I would be v happy.

Still no chance to try things out under dark sky BTW- temp of -25C at night here. Have to become a snow-bird I guess...

The Collins looks interesting but I think not at $4K (even if I could purchase it being non-USAian).

Edited by nosmoke (12/05/13 02:44 PM)


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acochran
professor emeritus


Reged: 06/19/08

Loc: So. CA
Re: How Big a Mirror Needed? new [Re: nosmoke]
      #6235780 - 12/05/13 04:57 PM

Quote:

Wow, if I could see that thru my future scope, I would be v happy.

Still no chance to try things out under dark sky BTW- temp of -25C at night here. Have to become a snow-bird I guess...

The Collins looks interesting but I think not at $4K (even if I could purchase it being non-USAian).



Here in the northern latitudes, Leo Triplet can be seen nicely in Spring/Summer evening skies, don't forget the Virgo cluster/right next to it, plus all those great galaxies by the Big Dipper...
Andy


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Kevdog
Pooh-Bah
*****

Reged: 07/11/12

Loc: Desert Hills, AZ
Re: How Big a Mirror Needed? new [Re: nosmoke]
      #6235928 - 12/05/13 06:11 PM

Quote:

Thanks for that interesting web site Kevdog. Looks like I'm in the purple zone (third brightest) but that was in 2006 (the apparent date of the map) so I'm guessing I am in the red zone now. Will have to get to darker skys when the opportunity arises.

Looks like a 16 or 18" might be wasted where I live so I would have to plan on travelling with it - maybe haul it on a small utility trailer and unload it via a ramp?




Purple is the 3rd darkest area. If you're in purple then you have good skies.
From darkest to brightest
Black
Grey
Dark Purple
Light Purple
Blue
Dark Green
Light Green
Dark Yellow
Light Yellow
Dark Orange
Light Orange
Dark Red
Light Red
White

There further away from the white areas, the better.

Try this one as well:
http://darksitefinder.com/maps/north-america.html

You can also use this outside to get a feeling of your Bortle Scale for your skies:
http://darkskydiary.wordpress.com/tag/bortle-scale/

Scroll down to the flow chart and follow along.

If you're in Orange or better, you can do some decent viewing at home (I know I do). But there's something magical about truly dark skies. But I'm not giving up the nights viewing at home either!


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MitchAlsup
Pooh-Bah


Reged: 08/31/09

Re: How Big a Mirror Needed? new [Re: nosmoke]
      #6235951 - 12/05/13 06:23 PM

Quote:

Thank you Mitch & Jay. When you say "fabulous" and "great", do you mean as good (or better) than the image?




Brighter than the image with somewhat smaller stars.


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Don H
sage


Reged: 12/28/06

Loc: Midwest US
Re: How Big a Mirror Needed? new [Re: nosmoke]
      #6236086 - 12/05/13 07:42 PM

Another thing to consider is your age and exit pupil size. I remember looking at these three galaxies many times at dark skies not too far from home in my late 30's and early 40's. All 3 were visible clearly with details in the same field with my 8" f/4.5 scope. I am 59 now, and while skies may not be as dark as back then, it is very tough to view all 3 in my 10", and they offer much less detail.

Regards,
Don


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nosmoke
super member


Reged: 11/06/13

Loc: Calgary, Alberta
Re: How Big a Mirror Needed? new [Re: Kevdog]
      #6236188 - 12/05/13 08:53 PM

Quote:

Purple is the 3rd darkest area. If you're in purple then you have good skies.




Woops, got my colours wrong - I am actually in the dark red (3rd brightest).


Quote:

Try this one as well:
http://darksitefinder.com/maps/north-america.html

You can also use this outside to get a feeling of your Bortle Scale for your skies:
http://darkskydiary.wordpress.com/tag/bortle-scale/

Scroll down to the flow chart and follow along.

If you're in Orange or better, you can do some decent viewing at home (I know I do). But there's something magical about truly dark skies. But I'm not giving up the nights viewing at home either!




Thanks, I will try the other sites above.


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nosmoke
super member


Reged: 11/06/13

Loc: Calgary, Alberta
Re: How Big a Mirror Needed? new [Re: acochran]
      #6236196 - 12/05/13 08:58 PM

Quote:

Quote:

Wow, if I could see that thru my future scope, I would be v happy.

Still no chance to try things out under dark sky BTW- temp of -25C at night here. Have to become a snow-bird I guess...

The Collins looks interesting but I think not at $4K (even if I could purchase it being non-USAian).



Here in the northern latitudes, Leo Triplet can be seen nicely in Spring/Summer evening skies, don't forget the Virgo cluster/right next to it, plus all those great galaxies by the Big Dipper...
Andy




Thanks Andy and from the looks of things, it may be spring b/f I can take a look anyhow...

Might be time enough to build a 16"er or so


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