400mm Focal Length Triple Scope Imaging System

[DIYASTRO]

I would suggest the 50mm to be used as a finder with a simple video or web cam as a 'finder' and the 135mm, or larger, to be used as primary guidescope.

You have already demonstrated that the mount is very good at tracking.... give it the chance to do what it is capable of and provide it with the tools It needs would be my advice.

Its the targets that don't have sufficient 'bright' points to use as guidestars that sometimes limit what we can image, increasing guidescope objective cannot be a bad thing!

Boyd

[Xplode]

I think a finder would be a waste of time implenting when you're already using Astrotortilla.

The 135mm would work great for a guidescope and so would most of your lenses.

I image at 1000mm with a 300mm f/4 Super-Multi-Coated Takumar guidescope and have also used a EF 200 2.8 and a 200mm f/4 SMC Pentax. All have worked perfectly.

If you go for a M42 lens i suggest you use a C thread to M42 adapter for max stability.

Here's my setup

[Gina]

I would suggest the 50mm to be used as a finder with a simple video or web cam as a 'finder' and the 135mm, or larger, to be used as primary guidescope.

You have already demonstrated that the mount is very good at tracking.... give it the chance to do what it is capable of and provide it with the tools It needs would be my advice.

Its the targets that don't have sufficient 'bright' points to use as guidestars that sometimes limit what we can image, increasing guidescope objective cannot be a bad thing!

Boyd

I've used an electronic finder in the past but nowadays I simply don't use a finder at all.  I run CdC, connect to mount (software calls it "Telescope"), slew to required target and then use AT for final alignment.  That puts my target precisely in the centre of my image sensor.

I tend to agree about using a 135mm f2.5 lens for guiding.  The consensus seems to be that the FL would be perfectly fine.

[Gina]

I think a finder would be a waste of time implenting when you're already using Astrotortilla.

The 135mm would work great for a guidescope and so would most of your lenses.

I image at 1000mm with a 300mm f/4 Super-Multi-Coated Takumar guidescope and have also used a EF 200 2.8 and a 200mm f/4 SMC Pentax. All have worked perfectly.

If you go for a M42 lens i suggest you use a C thread to M42 adapter for max stability.

Here's my setup

Thanks   Agreed - finder is surplus to requirements.

[Dave Lloyd]

Sorry Dave but I don't understand why you would want to do that. The point of multiple scopes is to take more than one image at a time, in different colours. The opposite might make sense viz. splitting the light from one scope onto several image sensors. In fact I believe this has been

done using dichrioc mirrors.

Ha ha, this is my total lack of experience in astrophotography showing. I wondered that as the images from the cameras would be combined by software to produce a composite, it might be possible to cut out the middle man as it were and combine them on the sensor. I suppose though that would give you far less control over post processing.

[Gina]

No, I don't think so.  The idea is to add the sensitivity and dynamic range of say 3 image sensors to give the effect of 3 times the exposure.  Each sensor is mono and every pixel is used to give the maximum possible sensitivity and resolution.

[Dave Lloyd]

No, I don't think so. The idea is to add the sensitivity and dynamic range of say 3 image sensors to give the effect of 3 times the exposure. Each sensor is mono and every pixel is used to give the maximum possible sensitivity and resolution.

Thanks Gina, it's just clicked.

[Gina]

Back to guiding...

I already have an adapter to connect an M42 lens to T2 thread and I use a Baader ClickLock to hold the LodeStar guide camera.  This is what I use with my OAG on the MN190 and it works perfectly (the ClickLock allows the camera to be unlocked and slid in or out to focus as the OAG doesn't have guide camera focussing).  The adapter to connect an M42 lens to T2 thread shown below also contains a filter slot which isn't needed in this application.

This photo shows the whole lens/camera assembly but without mounting system.  I shall need to design something.

[DIYASTRO]

Hi Gina,

Nice to see your choice of guide scope is to be the 135mm.

The 135 f2.5 was always a cracking lens, I have some too and a great lens  for guiding.

In fact, I have seldom come across a bad Pentax Tak  at any focal length. I particularly like the 50mm F1.2

Combined with your loadstar you should have perfect guiding capability.

I still like to have a 'finder /camera system' with my rigs, just like to see a wide field image of the area I am looking at and get my single semi active brain cell to comprehend the 'orientation' of the rig in relation to what I am trying to image.

Boyd

[Gina]

Update :-

Yet another project that hasn't seen the light of day for some time due to the weather!  It's all in a large cardboard box ATM.  In line with my end-of-year project progress analysis, I'll open the box and check.

[Gina]

In view of my decision not to sell any of my Atik 460EX mono CCD cameras I shall be resurrecting this project in due course, in line with my project schedule when I sort it out.  I want to get a couple or three other projects out of the way before resuming this one.  The weather needs to improve too

[Gina]

Well, the weather has improved overall - at least not continuous rain and more dry weather - I'm just hoping it continues   Anyway, I'm looking over my imaging rig projects and seeing what is wanted for each then I can see which looks the most promising for an early finish.  I'm trying hard to get my enthusiasm for imaging back

From what I can see, all that's needed to get this project working is to attach the guide system to the underside of the main ali plate.  I think I'll haul the rig out of it's box tomorrow and see what's what.

[Davey-T]

One of my favourite projects of yours Gina, I was getting pretty [removed word] with the weather but had two good nights recently and revived my enthusiasm, now can't wait for the Moon to 'opit for some more imaging.

Dave

[Gina]

Heavy rain again   Local forecast for the next 5 days is not good either.  They were forecasting a clear night for tomorrow but now it's down to a couple of hours followed by cloud and then rain.  That puts an overnight imaging run out of the question.  I need to be pretty sure of a full night without chance of rain before risking it.  Some time in the future I hope to have the roof automated with automatic closing if rain is detected (or maybe even cloud).  Unfortunately, my projects seem to be taking longer and longer as I get older

Right... back to the project...  I have struggled to lift the rig out of the cardboard box and onto the table - man it's heavy!!   And thats's without another couple of Kg of cameras, dew shields, etc.  Unfortunately, there's more to do than I thought from a cursary glance of it in its box.  The electronics box needs completing.  The box is there containing an Arduino Mega 2560, a bank of fuseholders and connectors for dew heaters and power input on the box.  The stepper motors for focussing the telescopes are connected to the Arduino and a couple of wires for power but nothing else.  I though I had this rig working a while back but must have had problems and changed the design.

Here is a list of jobs I see as needing doing before I can do any imaging :-

1. Wire up electronics box.
2. Design and make brackets to mount guide system to underside of main aluminium plate.
3. Replace a broken bracket for alignment of one of the ST80s.
4. Make dew heaters for the three scopes and guider lens.

[Gina]

Clear sky forecast for tomorrow night and it would make a nice change to do some astro imaging.  I would very much like to get this rig working but whether there is any chance of having it ready for tomorrow night is questionable.  I think the little UP Plus 2 3d printer is still working well enough to make the brackets required but I don't think I have the materials for the dew heaters - probably need to buy some Nichrome wire.

I may have a re-think on the electronics box - I would like a common box to use with all rigs used on the EQ8 mount - it seems nonsense to have separate boxes, all with fuses and focuser control electronics plus USB hub.  I have been trying to reduce cabling to a minimum, particularly cables that are required to bend when tracking and slewing.  With this in mind I have put the USB hub, remote focussing system and power distribution separately on each rig.  Then just three cables move about as the mount moves - main power, USB from computer and serial to mount.

One thing that has brought the idea of a common box to the forefront is that I'm thinking of buying a high quality USB hub and really only want to buy one of them.  I know probably the majority of imagers have their power and data distribution box on the pier and then run a whole bunch of cables to the scope or group of scopes but I would prefer to avoid umpteen cables that are required to move all over the place increasing the chance of breakage or porr connections.  I think a compromise would be to make a box that can be attached to whichever scope or multi rig I want to use.

 

[Gina]

I've ordered the StarTech rugged industrial 7 port USB hub from Amazon so I'll wait for that before finalising my power and data box.  I'm sick and tired of USB problems!

[Gina]

I've 3D printed a new adjuster bracket and replaced the broken one.

[Davey-T]

Recently bought a StarTech 7way USB3 hub to stick on the portable setup tripod so only one lead from the mount to the laptop, not had much use due to the inclement weather but seems to work well, only downside is the array of blazing blue lights

Dave

[Gina]

Designed and printed a pair of brackets for the guider - 135mm f2.5 Asahi Super Takumar lens and Lodestar X2 guide camera plus some adapters etc.  I'll take and post a photo when my camera battery has recharged.

Looked up the FOV for the Lodestar with 135mm lens and it's around 2° (2.62° x 2.02°) so should cover plenty of stars for guiding without any need to alter the alignment.  If I find any problem I can change a bracket to add adjuster screws.

[Gina]

The StarTech hub has arrived and it really looks the business   Proper job   Now I can design my data and power distribution box.

[Gina]

Next I ned to sort out what I want my data and power distribution box to contain.  Power input is via a 4 way XLR socket.  Data via a USB cable.  For control I need 3 stepper motor drives for focussing the three scopes - manual control should be sufficient for the guider.  I had thought of making my own dew power controller but I already have a 4 way Hitecastro box so why not use that and save myself some work?   I have a 4way "Y" cable for powering the cameras (3 Atik 460EX) with the standard concentric power plugs.  The dew heater controller has 2 12v similar sockets.

The StarTech USB hub has 7 ports.  I require 1 for the mount, 3 for the 460EX cameras, 1 for the Lodestar and 1 for the Arduino - making 6.  One spare   I shall require some fuses.  One for all the dew heaters and cameras in the supply line to the Hitechastro dew controller, another for the focus motors and probably one for the Arduino.  I might decide to separate the cameras from the dew heaters and use a separate camera power socket rather than the ones on the dew control box.

 

[Gina]

Post gone missing again   Now I've forgotten what I said

[Gina]

I'll see if I can remember what I posted...  Quite a lot as it happens something like 12 lines

Checking on the rig I find the "Y" cable isn't long enough to reach across the three cameras so I shall use separate cables for the power.  To reduce connections as much as possible I shall not use connectors at the box but take the cables inside through grommets.  It also means I can fuse each camera separately, which I like.

The USB hub will be positioned with the USB port side up to the inside of the box so that I can access the ports directly.  The power of the hub will be connected by wires going back inside the box to another fuse.  One USB cable will also go back inside the box to connect to the Arduino.

The dew control box I plan to attach to the outside of the box and feed it's power cable inside to yet another fuse.

The stepper motors that drive the focusers on the scopes are the ubiquitous 28BYJ-48 motors and require 5 wires (4 data and power).  The wires go straight inside the motors and are something like 6" long so these will need extending and connectors used where they go into the control box.  I therefore need to source some suitable connectors.  XLR would seem to be best from the reliability point of view but there may be alternatives.

These connectors look interesting - Sets Kits Electrical Waterproof Connector 1 2 3 4 5 6 Pin Way seal Car Boat wire

[Pan Euro]

They are good connecters as i have used them on both my land rover and motorcycles and never had a problem with them.

Ed