Thoughts on which imaging rigs to concentrate on

[Gina]

This is the final Ha sub of the series of 200 giving a total of 200 x 60s = 200m = 3h 20m total imaging time on the Ha - should be usable

[Gina]

Forecast is good again for tonight and I don't want to waste it.  OTOH I think I'm suffering from loss of sleep and can't just stay up all night like I used to when I was younger.  "Night shift" just doesn't seem to suit me   I have a fair collection of subs for M31 at this FOV I reckon and rather than doing 3 or 4 sets of subs overnight I would be better off doing one continuous run or maybe two parts with a meridian flip between.  Meridian flips are a nuisance and one reason I fancy a different mount - the EQ8 comes to a full stop just past the meridian.  I haven't automated a meridian flip yet

[Gina]

This new camera with it's 16MPx sensor and 32MB images sure gathers a lot of data!!  Particularly with hundreds of sub exposures of around a minute!!   I have now filled up a whole 2TB HD on my new desktop PC!   Will have to do some pruning.  I'm going to have to be more rigorous during runs and just afterwards and immediately dump any unwanted data.  Also, sets of biases, darks and flats can be dumped once they have been used to create masters.  I was about to calibrate the flats I collected the other day ready to process my RGB + Ha data for M31 and making space on the SSD by moving data from there to HD when I go an HD full error!!!

[Gina]

Now concentrating on the Cygnus Loop in 3nm NB and currently capturing Ha subs.  Done a bit of experimenting with gain and exposure and decided to reduce the gain by 6dB.  This seems to give a slightly better image.  Here is a single sub of 60s exposure and gain of 440 (44dB) T = -30°C.

[Gina]

The sky went poor for a while but it seems much better now.  Here's the latest 60s sub in Ha.

[Gina]

Now taking OIII subs following a meridian flip.  Still using 60s exposures and same gain.  Here is one - stretched in Photoshop.  On my new Linux desktop, PixInsight is currently calibrating flats.

[Gina]

Imaging in a clear sky   Cygnus Loop continued.  More OIII 60s subs at -29°C.  Here's a sample...  Oops wants flipping.

Edited October 11, 2016 by Gina

[Gina]

Captured 70+ OIII subs then a meridian flip and now capturing SII subs.  With the much fainter SII I've increased exposure to 120s per sub.  Here's an example, histogram stretched in Photoshop. 

[cosmojaydee]

On 10/10/2016 at 18:23, Gina said:

This new camera with it's 16MPx sensor and 32MB images sure gathers a lot of data!!  Particularly with hundreds of sub exposures of around a minute!!   I have now filled up a whole 2TB HD on my new desktop PC!   Will have to do some pruning.  I'm going to have to be more rigorous during runs and just afterwards and immediately dump any unwanted data.  Also, sets of biases, darks and flats can be dumped once they have been used to create masters.  I was about to calibrate the flats I collected the other day ready to process my RGB + Ha data for M31 and making space on the SSD by moving data from there to HD when I go an HD full error!!!

Hi Gina, would it not be better to transfer your data onto a blank CD ,that way you can store all your data and start a library all nice and neat 

[ChrisLX200]

I recently bought this offer from Maplins (that's right Maplins ) http://www.maplin.co.uk/p/seagate-backup-plus-hub-8tb-external-desktop-hard-drive-a07wj

8TB of extra storage for £209, pretty cheap I think. Works well. The drive inside is a Seagate Archive 8TB drive and even with the USB3 enclosure (with a built-in USB3 hub) it's still cheaper than the bare drive price elsewhere. It's not exactly the fastest drive ever but I transferred 260GB last night @ 109MB/sec which is perfectly OK for the purpose. I'll be using this to store my nightly AllSky camera videos which are starting to take up a lot of disk space.

ChrisH

[Gina]

Nice thought but two problems with that - CDs or even DVDs don't have the capacity and I keep enough rubbish without adding to it and there's the cost - that's three   A run of 100 subs is 3.2GB and I may capture several sets in a night amounting to 10-20GB.  A CD will hold only 700MB and a standard DVD 4.7GB.  Data compression doesn't help a lot.

[Gina]

With clear sky forecast for tonight I opened the roof and pointed the rig at the NAN in Cygnus.  Well it was clear just long enough to roughly frame the image and focus - then the clouds came in and have been here since.  I'll probably give up shortly and have an early night.

[Gina]

Cloud forecast for tonight and I've been out at a social event - guess what... - come home and clear sky!!  Hence now running an imaging session on the NAN & Pelican, currently 30s Ha subs with gain of 440 (44dB) and temperature reading -33°C - who says the minimum temperature is -30C

Here's a single sub histogram stretched in Photoshop - full frame.  Field seems nice and flat   Star size is 2-3px over the whole frame though some brighter stars are spreading a bit.

[Gina]

Now moved on to OIII subs but the OIII is much fainter.  Doubled the exposure to 60s but still not getting all that much - might double it again...

[Demonperformer]

The Ha is great, but what's caused the "splodge" in the upper left of you OIII sub - don't remember seeing that in previous OIII subs you have posted? Was it on all of them?

5 hours ago, Gina said:

who says the minimum temperature is -30C

What we really need is someone with access to a walk-in freezer, who can test it in really cold conditions ... or maybe we will get those conditions outside ourselves in a couple of months ?

[Gina]

I'm pretty sure the "splodge" is a dust bunny - a spec of dust on the camera window, judging by its size.  It has been present for a while but only shows really badly on this latest OIII sub due to a much greater histogram stretch to show the nebula.  I'll be investigating but first I shall take a set of flats to see if it will calibrate out of the data I've already captured.

As for temperature, I was thinking of testing it in my freezer.

Edited October 14, 2016 by Gina

[Gina]

Mainly clear tonight in spite of the forecast saying otherwise but with a full moon.  Imaging NAN & Pelican in OIII.  60s subs gain of 500 and temperature of -29C.

[Gina]

Clouds came in before the imaging run finished so closed roof and packed up.  Some more data to add to what I've got anyway   Didn't expect any tonight so it's a bonus

[wimvb]

Is it a full moon again? I hadn't even noticed with all the clouds we're having. Nice to see that you got some imaging time

[Gina]

Clear sky for a while and capturing more OIII data for the NAN&P.

Edited October 16, 2016 by Gina

[Gina]

I hope to do some image processing on all the data I've collected soon but I need to make some room for data files.  Meanwhile, I'm concentrating on the Linux and Raspberry Pi control and imaging system and also looking into where I shall be going with regard to FOV and DSOs to image.  I have a 45mm focal length medium format lens to try out once the adapter I ordered arrives.

Here's a list of focal lengths and fields of view :-

1. 45mm lens --- 1309m x 1005m   22° x 17°
2. 55mm lens --- 1071m x 823m    18° x 14°
3. 135mm lens --- 433m x 335m    7.2° x 5.6°
4. 200mm lens --- 295m x 226m    4.9° x 3.8°
5. 400mm scope - 147m x 113m    2.5° x 1.9°

Edited October 17, 2016 by Gina

[Demonperformer]

Wow! That 45mm lens will get some chunk of sky. Should give some great results.

[Gina]

Looks like the Heart & Soul Nebulae in Cassiopeia should fit nicely in the 135mm lens FOV

[Gina]

I forgot the 28mm f3.5 lens but I need to sort out the field flatness with that.  I think I have a 300mm f5.6 telephoto lens somewhere but it's a monster.

Here's the new list of focal lengths and fields of view :-

1. 28mm f3.5 lens --- 2103m x 1322m  35° x 22°
2. 45mm f2.8 lens --- 1309m x 1005m   22° x 17°
3. 55mm f1.8 lens ----- 1071m x 823m   18° x 14°
4. 135mm f2.5 lens ----- 433m x 335m   7.2° x 5.6°
5. 200mm f4 lens ------- 295m x 226m   4.9° x 3.8°
6. 400mm f5 scope ----- 147m x 113m   2.5° x 1.9°
7. 1.0m f5.3 scope --------- 59m x 45m  1.0° x 0.75°

Edited October 17, 2016 by Gina

[Gina]

There is a bit of a gap between the 200mm lens and 400mm Esprit 80ED scope so maybe I should think about the 300mm f5.6 lens.  I've had a look at shorter focal length scopes than the Esprit 80ED but we are getting into the more expensive makes.