Recently Browsing 0 members
No registered users viewing this page.
I have for sale my Skywatcher Startravel 120. Objective lens 120mm; Focal length . It is in excellent condition, clean and only very minor marks. Clean optics, no fungus. The focusser is the original one and works smoothly; 1.25" and 2" adaptors. With both caps.
A very good starter scope, or good as a portable scope.
Included accessories: red dot finder; 90 degree star diagonal; 10mm & 25mm EPs; mobile phone adaptor. All in as new condition.
Please don't ask me to split this package.
Price £140.00 no offers.
It will be very well packed.
Payment: paypal or bank transfer
I can deliver by Hermes; I can get a quotation for this if you wish. Or you can make your own courier arrangement, or collect in person.
Please PM me if you would like more information.
I was thinking, does an apo produce better images than an achromatic refractor for narrow band imaging? Chromatic aberration should not be an issue for NB but I read somewhere that for apo's spherical aberration is corrected for two wavelengths vs one for achromats.
So I am fairly new to the hobby, what I mean is I have a Celestron Astromaster 114 right now but its hard to use because of the non computerized equatorial mount as well as the red dot sight is bad. I am mainly interested in looking at DSO’s because they seem very interesting. My question is should i get a refractor or sct for observing dso’s and sometimes planets? I want a computerized one with tracking so I don’t have to take a long time finding nebulae and galaxies. Also, is there a certain type of filter to see color on nebula when not using eaa and just viewing with your eyes? I am looking to spend between $600-900
TS Optics Photoline 90mm Triplet
On reflection (or should that be through the lens of reality?) this was overpriced at £800, so is now reduced accordingly
In excellent condition, I gave a small writeup about this when I bought it, and it is still an excellent scope. However it has been losing out to the 60 and 76 Tak and now spends all of its time alone, safely flight-cased.
Don't leave this scope to suffer a lonely and unused life. Buy it and catch some great views this winter!
Payment: PayPal (buyer pays fees) or bank transfer (preferred).
Postage: Not included. Collection from Nottingham, UK is free (of course), otherwise you will need to arrange your own courier.
I have already posted my first astrophotographic session report in the telescope review thread: Tecnosky 80/480 APO FPL53 Triplet OWL Series - Review. But since that is more of a general review/diary of my experience with the new telescope, I feel some of the issues I am having are being buried and they will probably get more visibility if I post them - in a more synthetic version - in a dedicated thread.
So, a few nights ago (October, the 5th) I took out my new telescope for its first light. All the photos have been taken with the 0.8x flattener/reducer and the Optolong L-Pro 2" filter attached to the reducer. The camera is an astromodified Nikon D5300. The only processing the following pictures have consists in this:
Here we have a 90s shot of M31.
And here's a mosaic generated with the AberrationInspector script.
What I do like:
- tightest, smallest, roundest stars I have gotten since I started doing astrophotography at the end of January. Obviously comparing it to what I have been achieving with a kit 70-300mm zoom lens, these can't be anything else but better by orders of magnitude
What I don't like:
- star shape not consistent in all areas of the image
- residual chromatic aberration, especially on stars that are not round: there's clearly some red and blue edges visible
I didn't expect this from an apochromatic refractor, but maybe it's just because the stars are kinda "smeared", so not all light is focused at the same spot? I don't see this around the center of the image (or, at least, the problem is less pronounced). Maybe I have some tilting in my imaging train/sensor?
I have been doing some reasoning about it and it seems like a combination of tilting and/or backfocus spacing. According to the following image about backfocus spacing:
if the stars are elongated radially, the sensor is too close, if they are elongated tangentially, the sensor is too far. But to me it seems I have a little bit of both: in the top right corner, for example, the stars look radially elongated, in the bottom right, they look tangentially elongated. Top left they look tangentially elongated, bottom left also, but a little less. Seems like there has to be some tilting as well, otherwise they would all have a symmetric shape on all corners, correct?
How do I determine - is there even a way - if the issue is due to tilting only, backfocus only, or the combination of the two? Is there a sure proof way of checking for tilting? Like, rotating the camera and taking pictures with, say, the camera at 0°, 90°, 270° and 360°? If there's tilting, the pattern of the star shapes should follow the camera, correct?
I also tried splitting the channels in R, G, and B components, doing a star alignment of the blue and red channels with the green as a reference, and recombining the channels. The blue and red edges become a lot less evident, which is good, but obviously the star shapes remain the same.
In my Telescopius gallery you can also find two other images, Capella and Capella Mosaic showing pretty much the same issues.
Also, one issue with the guide camera: ZWO ASI 224MC. When attached to the guide scope (Artesky UltraGuide 60mm f/4), I can't seem to get a "sharp" focus, I even tried on the Moon, and the best I got was a soft lunar disc, with some major features visible, mainly by change of color/brightness (the maria, for example), but no details. The image still seemed blurred/bloated. Is it because of lack of IR blocking filter? I tried the same camera attached to the main refractor, with the L-Pro filter (which blocks UV and IR, as well) and I could focus perfectly. Do I need an IR block filter for guiding or even if the stars appear a little soft, the camera guides just fine?