Gina

Interesting Wonder if I can part my 10mm from the Pentax thread adapter...

"Ma bwain hurts Bwian"!!!

My M48 to M42 (T2) adapter measures 9mm and yes - taken into account. I'm measuring real distances with my steel rule. So 5mm over is better than 3mm under Maybe a little bit over would be alright. Found a 7.5mm T2 extension. Let's see what that can do... 27.5-7.5 = 20mm. Take off 9mm for the M48 adapter is 11mm. Done some more accurate measuring with my digital calipers. Short M48 to T2 is 8.8mm. Long M48 to T2 adapter is 18.5mm then I have 7.5mm and 15mm ones and a 10mm which seems welded to my M42/1mm to M42/0.75(T2) adapter.

Thanks Ken I'd forgotten about the 1mm for the filter... FLO sell a 12-14mm adjustable extension and another which can be set between 31.5mm and 42.5mm. The so called 10mm M48 to T2 adapter is actually nearer 9mm by my measurement. So the extra T2 extension required is 27.5-9 = 18.5mm. I have an OAG measuring 16mm. 2.5mm is still too much to get by using Baader spacer rings! Wish my lathe was good enough to turn 0.75mm pitch threads but it isn't - I've tried it.

Another combination gives 44mm. +6.5mm = 50.5mm leaving 4.4mm - groan... I wonder how well the Esprit works without the FF - this isn't the biggest of camera frames. BTW - I see there's some field curvature in your images Ken - is that without FF or have you got the back spacing wrong?

Found another (longer) M48 to T2 adapter that gives a distance from FF mating surface to EFW camera face of 39mm. Adding the 6.5 back focus = 45.5mm. That leaves 9.4mm. Hmm... As has been said before - however many extension tubes you have, you never have the right combination for what you went

Skywatcher Field Flattener for Esprit-80 - The spacing for dedicated CCD imaging cameras is 54.9mm from mating surface (75mm from centre of rear element). The rear thread is M48. When using T-threaded accessories you will need a FLO M48-T adapter. FLO M48 to T2 adapter - Adds 10 mm to optical path. ZWO Mini Electronic Filter Wheel (EFW) - 20mm front to back ZWO ASI1600MM-Cool USB 3.0 Mono Camera - 6.5mm back focus Calculation :- 10+20+6.5 = 36.5 54.9-36.5 = 18.4mm

Drat lost the post with all the data

Looking into getting the right back focus for the Esprit FF. I've found an M48 to T2 adapter so I can use the ZWO EFW mini but I think I may need some extra spacing.

I see - OK. I'll see what I can find.

I've been looking out the bits to go with the Esprit. As I recall I had all the bits to give the right back focus for the field flattener using the SX EFW with OAG. I adapted the SX EFW to fit the FF.

I've found that increasing the gain and decreasing the exposure gives better results. Of course this increasing data processing time considerably but a few hundred frames is not too bad with my fast Linux Mint desktop. I find processing with PI in Linux is much faster than Photoshop on my Win7 desktop. A faster machine plus faster OS makes a big difference Admittedly, I have found 60s exposures gives good results generally but mostly I have been imaging fainter DSOs. I think I'll probably use 30s exposures as a compromise. Have you found any SII in the Rosette? I know it emits Ha, NII and OIII and that would probably do for the 3 colours. I could see considerable NII in the widefield images with Ha 5nm - Ha 3nm and I've seen Ha, NII, OIII combination in published images.

If I were to increase the gain from the 300 that you're using I should be able to considerably reduce the exposure time and maybe capture unguided. I can get 5m with 135mm lens and a 400mm is about 3x as long so should be able to use 60s at 400mm unguided Seems the Rosette is brighter than I thought 15s exposure would want an extra 12dB gain (I think) meaning a gain setting of 420. Going down to 10s would mean a further gain increase of just over 3dB. ie. 450. However, with the KStars/Ekos/INDI system a download takes 8s for a setting of 16bit data so reducing the exposure too much would loose too much overall imaging time. A 16s exposure time would mean losing a third of the total time downloading at least until I can work out how to buffer the data and download during the next capture period. It doesn't do that as INDI and ASI driver is ATM - I've tried it.

Thanks very much Ken That looks very promising - great images That settles it - Rosette imaging with Esprit.

Do you have an image you could show me of the Rosette with 400mm FL and ASI1600MM-Cool please? Maybe it's time to work on my Esprit 80ED with field flattener + SX EFW with OAG + ASI1600MM-C. Might be worth seeing if I can get away without guiding

Been looking at what I would like to image and DSOs that need capturing soon if I'm going to get them this season. One I particularly like is the Rosette Nebula plus the Orion Sword including the HorseHead and Ha nebulosity in the area which fits in the 135mm lens quite nicely for a wide view. Also, as far as equipment is concerned I would like to try zoom lenses to see if they are up to DSO imaging. The Rosette Nebula would be a good candidate for the 75-300mm lens, with maximum magnification of 300mm. At that zoom the aperture is f5.6 similar to my Esprit 80ED scope which is 400mm but I doubt the lens would be anything like as good as the scope. Here's a screenshot of CdC and the Rosette Nebula showing frames of 200mm and 400mm focal lengths. I would like to be sure of getting the whole nebula in the FOV plus a bit of space around it, so I think 400mm might be a bit too much. OTOH 200mm looks like being too wide. So 300mm, in between the two would seem to be a good focal length to try.

I get over the CA problem with these vintage terrestrial lenses by imaging in narrowband.

I have found my box of lenses These include a Russian made Jupiter 9 85mm f2 lens which is quite a heavy chunk of glass, plus zoom lenses 18-55mm, 35-105mm and 75-300mm all around f4-f5.6. The shortest and longest are Canon and the middle one a Vivitar with M42 thread. None of these lenses will fit in my current rotation rig but I knew I would need more than one variation on this rig. The stock Canon 18-55mm zoom lens has a possible problem for remote control - the focus ring moves in and out with the zoom so will need a long motor pinion so that the teeth of the gear attached to the focus ring can slide up and down the teeth of the pinion. I have still to test zoom lenses to see if they are of sufficient quality for imaging use and I guess I should make up a rig to test the zoom lenses before making special rotation rigs for these lenses.

I think I may have done something wrong installing the INDI driver for the BCM2835 or maybe not done something needed as I get an error when trying to use either of the Astroberry drivers I want when they call bcm2835_init. eg. pi@raspberrypi:~ $ indiserver -m 100 -vv indi_rpibrd 2017-01-27T18:49:04: startup: indiserver -m 100 -vv indi_rpibrd 2017-01-27T18:49:04: Driver indi_rpibrd: pid=2877 rfd=3 wfd=6 efd=7 2017-01-27T18:49:04: listening to port 7624 on fd 4 2017-01-27T18:49:04: Driver indi_rpibrd: sending <getProperties version='1.7'/> 2017-01-27T18:49:04: Driver indi_rpibrd: bcm2835_init: Unable to open /dev/mem: Permission denied Child process 2877 died

Installed indi-astroberry... pi@raspberrypi:/ $ cd /home/pi pi@raspberrypi:~ $ ls bcm2835-1.50 Desktop Downloads indi-astroberry_1.0.4-1_armhf.deb Pictures python_games Videos bcm2835-1.50.tar.gz Documents index.html Music Public Templates pi@raspberrypi:~ $ sudo dpkg -i indi-astroberry_*.deb Selecting previously unselected package indi-astroberry. (Reading database ... 152862 files and directories currently installed.) Preparing to unpack indi-astroberry_1.0.4-1_armhf.deb ... Unpacking indi-astroberry (1.0.4-1) ... Setting up indi-astroberry (1.0.4-1) ... pi@raspberrypi:~ $

Just installed the BCM2835 INDI driver and subversion which will enable me to get the source code for INDI drivers, modify and install later. sudo apt-get install subversion cmake libgps-dev wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.50.tar.gz tar xvfz bcm2835-1.50.tar.gz cd bcm2835-1.50 ./configure make sudo make install

Astroberry driver install... DEBIAN PACKAGE ================ 1) Download latest binary package from http://sourceforge.net/projects/astroberry/files/Astroberry/ 2) Install downloaded package $ dpkg -i indi-astroberry_*.deb

The weather didn't improve until after dark when the clouds dispersed and the fog in the valley didn't come over here. So there's a clear sky with masses of stars visible. Might have guessed - well I did guess and made the decision to look after my health rather than ambition! I know it was the right decision but I hate missing out on imaging time.

The clouds almost parted a little while ago and it looked like clearing but it changed its mind!! Now it's looking brighter again! The weather just can't make up its mind! Decision - leave the imaging rig all set up ready to go outside or strip it down and check how everything fits together again in the rotation rig. May be able to arrange it to be used with that without the RPi, using the same Arduino Nano and power circuit as it is now all connected to the laptop. This cold is still making me feel pretty grim so maybe it would be better just to abandon all thought of imaging tonight and stay in the warm. At least I can play about with the rotation rig If I were to set up outside I would need to take the laptop back out as well as the imaging rig so a couple of trips out into the cold and some time setting up in the cold observatory. I would have to do that in the daylight and before it got even colder and still the cloud or fog could come in. I'm currently watching Countdown and can usually beat the contestants from the comfort of my settee but I'm not doing very well today which shows I'm not up to scratch At least I've just solved the numbers, though so have the contestants

Well unless something quite magical happens to the weather I'm staying indoors in the warm!!