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Uranium235

More 130pds action - IC405 - IC410

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Quite literally hot off the telescope this one is. Another test to see if the other night wasnt some fluke, and so far tonight the 130pds hasnt put a foot wrong - though im giving it a tougher test now by asking it to get the seagull nebula... quite low and the Moon is now well up -  I will give it a couple of hours unbinned to see if I get anything worthy out of it.

Processing was pretty quick because I already had a bunch of new master calibration frames I made in the afternoon, so it was just a case of stitching them together and processing as normal... seems like I missed a bit though... doh!!  What was that about measure twice - cut once? Oh well, its only bit of a test really :)   Its unlikely the camera will be disturbed so I might come back to it for more subs, just to get the noise down in the dimmer parts of the nebulosity. Suppose I cant really argue for just one hour per pane!

IC405 (Flaming star) + IC410 (Tadpoles)

8x450 (Ha) x2 panes  (2x2 binned)

130pds (0.89x), Atik 383, NEQ6

Setpoint: -30

Calib: Flats and Bias

Thanks for looking! :)

12549102443_17822313b5_b.jpg
7

Edited by Uranium235
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Great looking image. You really are getting the best out of a 130 - very nice indeed.

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Beautifully composed and such tight stars!

Cheers :)

The tightness of the bigger stars is down to using a layer mask on about 7 or 8 of the larger stars - it really helps to keep them under control when stretching the histogram.

The seagull is almost done now.... not holding out much hope, the stars are a litlle bit blobby down on the horizon.

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Great looking image. You really are getting the best out of a 130 - very nice indeed.

Thanks Michael, im just waiting for a properly dark night (or SGL9) so I can really give it the beans in LRGB or Ha/OIII.

If I were to use it at SGL9 without an LP filter (just UV/IR cut), I can see it being a real photon hoover (flats would be a nightmare though!).

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That just goes to show what can be achieved with a basic scope on a decent mount with an expensive camera :)

Lovely image by the way

Here's one I've just been sent from a friend in our local AS imaging group.  No idea of the exposures etc, but it was through an ED80 and a QSI camera (if memory serves me correctly)

post-10726-0-68120000-1392561903_thumb.j

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Ahhhh, its probably an 8300 based QSI - same as the Atik. Looks like a 2 pane mosaic to me as the 80ED is about 60mm shorter in FL than the 130pds (when both are reduced). If the 130 keeps knocking stuff like this out then im not sure whether the 80ED will get a look-in again - its sitting down in the basement at the moment looking rather sorry for itself...lol.

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Hi all,

I'd better own up to the coloured mosaic.

Yes, Uranium235, you are right. It's a two-pane mosaic slightly cropped to remove the mis-registration of images:

T: Equinox 80ED with a Televue TRF-2008 reducer to give 400mm focal length at F/5.

M: EQ6 with Rowan Astronomy belt drive mod.

C: QSI 583wsg with a Lodestar guider and Astrodon RGB and H-alpha (3 nm) filters

Captured on 11 and 13 Feb 2014 under almost full moon.

IC405 has 8 x 300s each of RGB and 3 x 1200s of Ha.

IC410 has 6 x 300s each RGB and 6 x 1200s of Ha.

Captured with Nebulosity, stacked with DSS and processed with Pixinsight, Nebulosity and Photoshop.

Cheers,

David

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Very nice, how did you find the actual flatness of your images when it came to stitching them together. With the 80ED, I found that even though the field looks flat - its just ever so slightly out if you dont leave enough overlap between panes. Ive since overcome that little problem, but it caused me a few headaches when I first switched to a full frame camera.

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Well I have to admit that this didn't begin with the intention of making a mosaic. I shot IC405 because I wanted to see what it was like.

At the same time I've been experimenting with the spacing of the RFL-2008 to eliminate coma stars in the comers. On IC405 the spacing is set slightly short and gives bean-shaped stars in the corners.

I took the camera off and set the spacing 0.5 mm longer and shot IC410. This gave a better result and my intention was then to reshoot IC405 with camera in the same orientation. But I've so far failed to do this.

I therefore put the mosaic together as an exercise to see if I could do it. Each image had different exposure, rotation and slight but different colour cast (nearby moon and no LPF).

So I have to admit that I'm not quite satisfied with the flatness of this setup.

When using the ED80 at its native F/6.2, I use a Teleskop Service flattener and get very good results from it. Unfortunately, it is now rare that I shot at the FOV that setup gives.

Thanks for the comments BTW.

David

Sent from my iPhone using Tapatalk

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davies07, on 16 Feb 2014 - 10:25 PM, said:

Well I have to admit that this didn't begin with the intention of making a mosaic. I shot IC405 because I wanted to see what it was like.

At the same time I've been experimenting with the spacing of the RFL-2008 to eliminate coma stars in the comers. On IC405 the spacing is set slightly short and gives bean-shaped stars in the corners.

I took the camera off and set the spacing 0.5 mm longer and shot IC410. This gave a better result and my intention was then to reshoot IC405 with camera in the same orientation. But I've so far failed to do this.

I therefore put the mosaic together as an exercise to see if I could do it. Each image had different exposure, rotation and slight but different colour cast (nearby moon and no LPF).

So I have to admit that I'm not quite satisfied with the flatness of this setup.

When using the ED80 at its native F/6.2, I use a Teleskop Service flattener and get very good results from it. Unfortunately, it is now rare that I shot at the FOV that setup gives.

Thanks for the comments BTW.

David

Sent from my iPhone using Tapatalk

The TV reducer takes quite a bit of tinkering to get exactly right (mine did), when using a CCD I always add 1mm (sometimes more) to the manufacturers suggested spacing distance, as you need to take into account the thickness of your filters and CCD window (both of which extend the lightpath by appox 0.3x their thickness). As we are finding out, trying to get a flat field on a big chip for a low price is a bit of a challenge.

How are you stitching the images together? I found MS ICE to be quite good at making a decent fist of a bent field, Registar also has some powerful dark magic up its sleeves and perform miracles on slightly curved fields.

I do have another update on the 130 (well, the corrector actually), while its quite sweet in narrowband - I cant say the same for LRGB. The stars are still round, and the field is still flat - but unfocused light or something else is getting in and creating a large circular artefact in the image - its also visible in the flats. Ahh, this is the downfall of the SW coma corrector - yes its fast, but is does a pants job in controling stray light in broadband imaging. Im guessing that the stray light must be of a particular wavelength as it is not visible in Ha data. The only way to find out would be to image in RGB and see which filter in which the artefact is strongest (my vote is blue). Would an additional anti-reflex UV/IR filter in front of the CC eliminate this?

For now, I will swap back to the Baader MkIII and put up with a slight loss of FOV (though enjoy refelection free imaging), but I can still 2x2 bin the camera and get an FR equivalent of approx f3.4, and a sampling rate of 3.4" p/p - a sampling rate not too dissimilar to that of a short FL refractor.

Edited by Uranium235

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This is really useful information. Thanks.

I've heard of packages like MS ICE and Registar for generating mosaics but I hadn't twigged that they will deal with curved fields and therefore can be very useful. I will have a look at them.

I blended these two images by hand using Nebulosity and Photoshop. In PS I stacked them and then used a mask on the top layer to feather the join.

You're absolutely right about the TV RFL-2008. I've been fiddling with this, off and on, for weeks and I'm still not satisfied with the results. Although I have taken into account the extra spacing I need for the filters, I can't seem to get the optimum spacing. Inspecting the IC410 image I still see bean-shaped stars in the corners. I think I need to increase the spacing a bit more. This, as you say, is the penalty for doing astro-photography on a relatively small budget. It's difficult, and there might not be an optimum solution if you are not using the Televue scope for which it was designed.

I used the Baader MPCC with a 200P and found it very good. I now use a Paracorr but I suspect that would be going in entirely the wrong direction for you: cost - it cost nearly as much as my scope - and it adds 15% to the focal length, further narrowing the FOV.

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