Jump to content


Photo

Edge 8" and TEC 140

  • Please log in to reply
20 replies to this topic

#1 HowardK

HowardK

    Apollo

  • *****
  • Posts: 1091
  • Joined: 20 Oct 2010

Posted 24 April 2013 - 03:25 AM

All

I am lucky to have an Edge 8" and a TEC 140 set up side by side.

What scope would the forum feel would give the better more pleasing view with premium eye pieces from a mag5 suburban backyard in poor seeing (3-4 Pickering) whilst observing Saturn at similar magnification of around x140?

Interested in people's comments

#2 JJK

JJK

    Surveyor 1

  • -----
  • Posts: 1990
  • Joined: 27 Apr 2008

Posted 24 April 2013 - 04:11 AM

TEC140

#3 bilgebay

bilgebay

    Skylab

  • *****
  • Moderators
  • Posts: 4200
  • Joined: 06 Nov 2008
  • Loc: Turkiye - Istanbul and Marmaris

Posted 24 April 2013 - 04:37 AM

+1

#4 Ira

Ira

    Mercury-Atlas

  • *****
  • Posts: 2625
  • Joined: 22 Aug 2010
  • Loc: Mitzpe Ramon, Israel

Posted 24 April 2013 - 05:14 AM

Why don't you take a look and let us know. :)

/Ira

#5 HowardK

HowardK

    Apollo

  • *****
  • Posts: 1091
  • Joined: 20 Oct 2010

Posted 24 April 2013 - 05:29 AM

I am more pleased with the Edge...

Saturn is brighter.......shades on the surface slightly more apparent

Cassini easily seen in both scopes....perhaps more delineated at the edge in the TEC...

is this because of the 8" compared to the 5.5" aperture?

#6 bilgebay

bilgebay

    Skylab

  • *****
  • Moderators
  • Posts: 4200
  • Joined: 06 Nov 2008
  • Loc: Turkiye - Istanbul and Marmaris

Posted 24 April 2013 - 05:36 AM

:confused: I am even more excited to see the first light through my new C8 Edge now :jump:

#7 HowardK

HowardK

    Apollo

  • *****
  • Posts: 1091
  • Joined: 20 Oct 2010

Posted 24 April 2013 - 05:46 AM

when will that happen Sed?

I want to hear your opinion

#8 bilgebay

bilgebay

    Skylab

  • *****
  • Moderators
  • Posts: 4200
  • Joined: 06 Nov 2008
  • Loc: Turkiye - Istanbul and Marmaris

Posted 24 April 2013 - 06:07 AM

Hopefully this weekend. But you know, there is this "new equipment curse" thing :)

#9 HowardK

HowardK

    Apollo

  • *****
  • Posts: 1091
  • Joined: 20 Oct 2010

Posted 24 April 2013 - 07:30 AM

Stay in touch then

#10 Eddgie

Eddgie

    Voyager 1

  • *****
  • Posts: 12702
  • Joined: 01 Feb 2006

Posted 24 April 2013 - 08:21 AM

Saturn is brighter.......shades on the surface slightly more apparent



First, to answer your question, I would think that for planets, they would be roughly similar.

But your quote indicates that you are seeing something that I have been saying for a very long time.

When people indluge in these debates about refractor/reflector, they often omit the human eye's contrast sensitivity threshold.

When used at the same power, a bigger scope gives a brighter image, and my own belief is that this brighter image is indeed a very helpful attribute in resolving low contrast detail.

I see the same thing with my 6" APO and EdgeHD 8".

At 180x, the image is quite a bit brighter in the EdgeHD 8" and as a result, I find it just easier to see the most difficult detail.

I give the nod to the 6" APO for having a bit better contrast, but only a tiny bit.

Aperture is your friend for planets.

Again, to answer your question, I would think that these would be fairly similar. If your EdgeHD has quality on par with mine (which is to say quite excellent), it should perform almost the same on Saturn at the focal plane.

But the brighter image may indeed give you the advantage in more easily seeing the detail present.

I say it over and over and over on these forums.. For planetary observing, good quality clear aperture is your friend.

Seeing is your enemy, not central obstruction, and patience is your best weapon.

#11 EFT

EFT

    Vendor - Deep Space Products

  • *****
  • Vendors
  • Posts: 2545
  • Joined: 07 May 2007
  • Loc: Phoenix, AZ

Posted 24 April 2013 - 10:01 AM

Hopefully this weekend. But you know, there is this "new equipment curse" thing :)


Sadat,

It was great to meet you at NEAF.

Ed.

#12 bilgebay

bilgebay

    Skylab

  • *****
  • Moderators
  • Posts: 4200
  • Joined: 06 Nov 2008
  • Loc: Turkiye - Istanbul and Marmaris

Posted 24 April 2013 - 10:37 AM

Likewise Ed, thank you :) I hope it has been a productive weekend for you. Seeing your daughter help you made me very happy as a father. She is great!

I will install the fans tonight although I will not hear them purr until Saturday. (Maybe they don't even purr :) ) .

Sedat.

#13 EFT

EFT

    Vendor - Deep Space Products

  • *****
  • Vendors
  • Posts: 2545
  • Joined: 07 May 2007
  • Loc: Phoenix, AZ

Posted 24 April 2013 - 10:44 AM

Likewise Ed, thank you :) I hope it has been a productive weekend for you. Seeing your daughter help you made me very happy as a father. She is great!

I will install the fans tonight although I will not hear them purr until Saturday. (Maybe they don't even purr :) ) .

Sedat.


Kendra did a great job and had a great time. She loves to meet and talk with people form all over. I was actually able to sit down and let her handle things at times. Mounts that can be run off of a tablet or smart phone are the perfect match for a teenager. She had never even used SkySafari before and was able to just jump right in and go.

#14 bilgebay

bilgebay

    Skylab

  • *****
  • Moderators
  • Posts: 4200
  • Joined: 06 Nov 2008
  • Loc: Turkiye - Istanbul and Marmaris

Posted 24 April 2013 - 10:47 AM

:) Lovely. You are both very lucky :)

Cheers

#15 bobhen

bobhen

    Viking 1

  • -----
  • Posts: 683
  • Joined: 25 Jun 2005

Posted 24 April 2013 - 11:04 AM

All

I am lucky to have an Edge 8" and a TEC 140 set up side by side.

What scope would the forum feel would give the better more pleasing view with premium eye pieces from a mag5 suburban backyard in poor seeing (3-4 Pickering) whilst observing Saturn at similar magnification of around x140?

Interested in people's comments




At 140-power (that’s kind of low for Saturn) you might not see much difference although the TEC should be sharper. As the seeing allows you to push to higher powers (say over 275 or so) the TEC will remain sharp while the SCT will start getting softer.

Bob

#16 HowardK

HowardK

    Apollo

  • *****
  • Posts: 1091
  • Joined: 20 Oct 2010

Posted 24 April 2013 - 11:05 AM

I can never go to that kind of magnification

My seeing is always 3-4 Pickering

#17 Eddgie

Eddgie

    Voyager 1

  • *****
  • Posts: 12702
  • Joined: 01 Feb 2006

Posted 24 April 2013 - 11:40 AM

That has not been my experience.

If seeing permits it, my EdgeHD 8" seems to take magnification as well as my 6" APO.

Better in fact, because at 270x, the image is getting dim and grainy in the 6" APO. It is in the 8" too, but not as bad.

Image brightness to me counts for a lot.

#18 RAKing

RAKing

    Fly Me to the Moon

  • *****
  • Posts: 6242
  • Joined: 28 Dec 2007
  • Loc: West of the D.C. Nebula

Posted 24 April 2013 - 11:41 AM

I can never go to that kind of magnification

My seeing is always 3-4 Pickering


Ugh! That's too bad. :p

To answer your original question - I had my TEC set up next to a C8 Edge at a public session a couple of years ago. Both scopes are great, but my TEC could easily see M76 while the Edge could just barely pick it out. I attribute that to the CO and loss of contrast at certain light levels. The Perseus Double was also much nicer through the TEC's FOV.

On the other hand, the larger aperture of the Edge allowed it to split a couple of the toughter double stars - such as Sirius B and A-B Zeta Cancri - that were a lot more difficult for the smaller TEC.

Both scopes deserve a place in your home. :cool:

Cheers,

Ron

#19 jrbarnett

jrbarnett

    Eyepiece Hooligan

  • *****
  • Posts: 20320
  • Joined: 28 Feb 2006
  • Loc: Petaluma, CA

Posted 24 April 2013 - 04:17 PM

8" vs. 5.5", resolution:

The 5.5" on paper can resolve down to 0.82 arc seconds.

The 8" on paper can resolve down to 0.57 arc seconds.

But the usefulness of the difference in resolving power depends on how often your seeing permits either 0.8 arc second or 0.5 arc second resolution. If not often then the resolution difference isn't likely that relevant in explaining differences seen between the two.

Do you recall what magnification/exit pupil each scope was operating at during your Saturn observations. Exit pupil diameter will affect visual image brightness. There are a number of reasons not related to optical quality that could explain the TEC's slight advantage in resolving the Cassini Division (a relatively easy task for a 70mm scope, by the way - not a remote challenge for either of your scopes). Thermal equilibrium would be the most likely non-quality related explanation. Collimation might be another.

Interesting report in any case. Last June I had a TEC 140 manhandle a C8, C11 and 15" Dob on Saturn. More detail was seen in the TEC than in any of these three other scopes (the 8" and 11" of which were mine and the 15" used to be mine, so I know most of what there is to know about each of these particular units). Multiple attendees commented that they had never seen a better Saturn in their lives. These were not noobs either. These were all veteran observers. I kind of had to agree though I thought the C8 put up the best fight of all of the others suggesting to me that seeing probably played a role in the results (two small scopes outgunned two much larger scopes; the opposite of what normally would be expected if "all else were equal").

But ultimately the scope that makes you happiest is the better choice for you. Best of all, the Edge runs a little over 1/5 the cost of the TEC. Imagine all the extra cash you'd have if you kept the Edge and sold the TEC. :grin:

Regards,

Jim

#20 jrbarnett

jrbarnett

    Eyepiece Hooligan

  • *****
  • Posts: 20320
  • Joined: 28 Feb 2006
  • Loc: Petaluma, CA

Posted 24 April 2013 - 04:37 PM

"On the other hand, the larger aperture of the Edge allowed it to split a couple of the toughter double stars - such as Sirius B and A-B Zeta Cancri - that were a lot more difficult for the smaller TEC."

That's the opposite of how things roll here in Sonoma County with Sirius B. Sirius B is easiest in 3" to 4" unobstructed scopes at moderate magnification 70-100x. Resolution is not an issue for Sirius B; the split is HUGE. 80% of the challenge is suppressing/controlling glare from the primary; 20% of the challenge is hoping the seeing is good enough to let you pull it off. A smaller aperture scope without a big scattering central obstruction does a better job keeping light where it belongs in the image, and is also less affected by shifts in seeing.

I have an 80mm LOMO that has the easiest time of all my scopes with Sirius B. They get progressively tougher as aperture increases. The only obstructed scope I own that has ever shown me Sirius B is a Mewlon 210, and in that case one of the spider arms was fortuitously places adjacent to the secondary star, making it easier to pick out.

It also seems to take more "brute force" magnification in a larger scope to pull off. The 3-incher does it consistently at 80x to 90x. The TEC likes 100-110x better. The Mewlon likes 200-230x better, etc.

I'd always heard that Sirius B took aperture and high magnification, and had never made a very serious effort to resolve it in any smaller scope. CNer Jared Wilson showed me the error of my past ways at a dark sky camp out in the Mojave in 2010. Jared decided to try Sirius B in his own 80mm LOMO, and I silently said to myself that he must be nuts - "everyone knows Sirius B takes aperture and high magnification". It was no problem in the 80mm at around 70x. The TEC (mine) took closer to 80-90x to do it, and didn't show it as constantly as the tiny LOMO. Seeing was really bad and it was windy. Not one single larger scope on hand (10", 11", 12" and 15") could do it at any magnification.

Moral of the lesson I learned? Little refractors are ideal tools for widely spaced but grossly unequal magnitude doubles. Try it!

Regards,

Jim

#21 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 8218
  • Joined: 08 Aug 2007
  • Loc: La Union, PI

Posted 24 April 2013 - 05:24 PM

Little refractors are ideal tools for widely spaced but grossly unequal magnitude doubles. Try it!

Regards,

Jim


I have, and it appears you raise a good point. It does seem my obstructed CAT struggles with unequal pairs, especially within a range of separations and deltaM. But, on close equal pairs it holds it's own. I have not been able to split the pup, either.

Still, it mathces closely descriptions and images of Jupiter from refractors an inch or two smaller in aperture. It stays well tuned and under pretty stable tropical skies. The seeing is regularly good enough to let it work at full aperture in terms of resolution and contrast. (Often, I thank God for those jaw dropping moments.)






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics