All SCT owner did you know this?

[rumples riot]

Hey all, this something I just learned and just wanted to find out that if you know.

Apparently the correct way of inserting a barlow for imaging and viewing is into the back of the scope first, then the diagonal and then the eyepiece or webcam. Without doing this you will get aberration and slightly blurry pictures. This would explain why I cannot get perfect focus as i have been inserting diagonal, then the barlow and finally the webcam.

Anyone else doing this?

[[1ponders] (Paul)]

Yes, I am using the barlow first. I found it gave a clearer image, plus (and this is only my subjective observation), I think you get a larger image. The only thing I have to watch is if I'm swinging towards the Zenith. OUCH!

[gbeal]

Paul,
news to me as well, but then again I'm not a big SCT sorta guy.
I use the barlow only if I can (in the Mewlon for example).
If there is a significant distance (as there will be with a diagonal) after the barlow then the stated amplification will not apply. It will be greater.
I understand there is a reference to this on the Televue site, specifically in regards to the Powermates.
Gary

[Comet Hunter]

When I'm viewing I have barlow then diagonal then eyepeice - main reason is to reduce the amount of weight hanging out the end. By having the barlow first the majority of the weight of the barlow is inside the OTA/microfocuser thus reducing overall weight in mid-air = less stress.

When imaging I dont use the diagonal at all - the less glass for the light to pass through the less chance of something dodgy happening to it - dirty lenses etc

[Robby]

When imaging I use barlow then camera..
For visual I now use a powermate and put it in after the diagonal because my diagonal is 2", so I have no choice. Seems to work alright in my 8" SCT. Perhaps I should try it before the diagonal and resurect the old 1.25" diagonal??
Perhaps tonight if the cloud stays away and the seeing allows.
Cheers

[rumples riot]

Well tested the theory out this morning and it is correct, image scale is larger and the image is much clearer. Just processing the shots now and am really happy with the base images. Much better than before. You all should try it, it does work.

[silvinator]

Fellas, I actually stumbled across this on the Meade web site whilst checking out the barlow specs and even they say it's true. This is the blurb for those who don't want to scroll all the way down:

With a diagonal mirror or prism placed between the Barlow and an eyepiece (e.g., in applications with refractors or Schmidt-Cassegrains), effective eyepiece magnification is approximately tripled.

[Strgazr27]

Originally posted by Comet Hunter
When I'm viewing I have barlow then diagonal then eyepeice - main reason is to reduce the amount of weight hanging out the end. By having the barlow first the majority of the weight of the barlow is inside the OTA/microfocuser thus reducing overall weight in mid-air = less stress.

When imaging I dont use the diagonal at all - the less glass for the light to pass through the less chance of something dodgy happening to it - dirty lenses etc

Andrew,

Your Barlow weighs less than your diagonal? I would check that as the weight of the diagonal+EP has got to be more than the Barlow+EP. This would especially be true of a prism Diag. I am just curious as my 2" Diag+ EP weighs A LOT more than the Barlow+EP. The least impact on balance and stress will come with the weight being placed as close to the center of the base/Forks as possible. In your arrangement the weight is moved out the difference in distance between the length of the barlow and the diag. Of course, all this is mute if the image is truly clearer with the Bar. first. The stress imparted is in no way great enough to allow it to impact visual performance. Like I said, just an observation I have made.

CS's

Bobby

[Comet Hunter]

Hi Bobby,

I'm using the 1.25" diagonal that came standard with my scope, my barlow is a 3x Televue, and my eyepieces are a set of 1.25" Meade Super Plossls from the eyepiece deal Meade had a year or two.

Firstly, sorry I should've been a bit more specific, I've only just recently bought the barlow and generally only use it for imaging, but when I do use the barlow for viewing I use the order I described. Having a full range of EP's gives no real advantage to use the barlow except for the eye relief it brings when viewing. Currently for me it's a trade off of no eye relief (not using the barlow) or more weight using the barlow when viewing, I'm trying to avoid the extra weight of the barlow when viewing for the moment as my scope is still requires fitment of a counter balance mod and with the full optical train of barlow + diag + EPs' it becomes VERY rear heavy. When I have added the counter balance I'll use the barlow more regularly when viewing.

Regarding the weights of each piece, I dont have any scales to accurately check the weights, but I would say my barlow would be slightly heavier then my diag. (I'm using the smaller 1.25" equip. remember).

This is my reasoning behind the order I use when I do view with the barlow.....

When inserting diag. first, only an inch or so is held inside the microfocuser, with next to no weight of the diag. inside the scope leaving most of the diag. weight + barlow + EP outside the scope. When inserting the barlow first about 2" are inside the microfocuser (in this 2" is all of the lense(s) of the barlow = large proportion of the barlow weight) thus only a small proportion of barlow + diag. + EP are outside.

I understand, and completely agree with having as much weight towards the pivot points to help create as much of a naturally balanced scope as possible, however having the diag. first with only that small amount of connector (approx. 1" in lenght) and basically no weight inside the scope and all that weight hanging in mid-air makes me a little uneasy when compared to having over a 1/3 of the barlow length (2" out of 5" total lenght) +most of its weight inside. I feel it gives more strenght to the optical train this way then diag. first approach. Each to their own though.