skybadger

Edmund optics sell the holographic transmission grating as an a4 sheet. That's exactly how I started doing spectroscopy before the star analyser came along. Somewhere I also have a thin wedge prism which was to be used to redirect the output spectrum back onto the optical axis. Never quite got around to mounting it. It's purpose was to solve the issue of only part of the spectrum ever being in focus at a time.

Me too but I also had 3 non- pointless. It's funny how you recall star names in detail after the time you need them .

I use the latest betas, they typically include feature requests I find useful, like the ability to use comet 2LEs to cause PhD to track properly on stars while imaging the comet.

I don't understand the reticence with ascom here, it's been very stable for a long time. Updates typically add features, like Alpaca since V6. It's good to hear that you had a simple job of getting ascom to talk alpaca to the indi bridge. I've invested a lot of time and effort into writing embedded alpaca devices and it's good to hear that they will also work with astroberry equivalents.

Does sgp support the ascom observing conditions interface ? That would be my route.

Clear the pillar and replace with steel column ? I can't see any guarantee of bonding to a new pour here but I guess high rise builders do that all the time too. My 12" diameter pier is 6' long and sits on a square plate bolted to the foundation block by resin fixed inserts.

You get to fewer number of bands by being closer to the point of focus, ie defocus only a little bit either side, you get more lines crowding in the further away you are from focus. At focus you've got zero lines and you're essentially taking a Foucault-gram. In taking a picture of a star I'd be looking for the airy rings to check they are centred, you can have the illuminated secondary centred in the beam but the primary and secondary reflections still be out.

Can you take a set of ronchi images that are three or 5 bands only, both inside, at and outside focus. The ones above are alarming but it might just be thermals and shows some sort of regular pattern from NW to SE that might be confusing. Also, what does an out of focus image look like on a bright star without the ronchi ? Ie how well collimated is it actually ? I guess you already know you are looking for parallel lines to indicate the correct mirror spacing and theres a good amount of contrast on the lines so the spacing looks fine to me... Other eyes will help.

Very nice. The feet for the dome shed is a lot like my first one, so a word of caution, over time they will sink unevenly and the top ring will deform to match. I really like what you've done with the thin ply. Did you consider fibre glassing the outside Vs 2-part epoxy paint ? Very nice construction . Well done.

Reading this makes me feel we need an astronomers dark sky cam network so peeps can see what the sky is like at their chosen target location . Does promise it will be the same when you get there though. I do find that the met office forecast is good enough for that though.

I don't think the gamepad code in eqmod is listening for a Bluetooth device. I suspect the answer is an intermediary device that turn the device into appearing as a usb.

Have you tried passing the ring through a bike inner tube to provide the grip. It solved a similar problem I had. Needs some silicone to get the tube over the ring though.

I don't know about anyone else but right about now, a warm autumn day cooling towards winter , is when the bugs invade and jam up wheels, hide under all corners and worm into places they shouldn't be So I invested in this stuff to both preemptively and as a dispersal spray, kepp them out of the holes. https://www.amazon.co.uk/gp/aw/d/B004W2FUWK?psc=1&ref=ppx_pop_mob_b_asin_title And so far it's working. My daughter says it's used on horses and wears off /evaporates but it's working so far. There's nothing I hate more than opening up the dome and getting showered with ladybirds that then go scuttling into collars and pockets. Better than conkers.

I find that it depends.... Typically it's always clear below -18C It's always cloudy above 5C It's in between where it can be tricky. I've had nights where the sky temp has been above zero and they were still clearer than other nights where it was below -5. I believed it was due to the direction of the prevailing wind at the time, bringing different bulk masses of air at different temperatures and humidities. If the air temperature is warmer than usual due to say coming up from the Sahara, it can still be clear and quite warm. If it's from the north or north east (for the UK) the air tends to be quite cold when it's clear. Which is when the -18 figure might be the useful figure. I have encoded this into my safety driver but what I really want to finish is my star detecror/cloud coverage estimator on the all sky camera.

Fair point.

Nothing indicated on aurorawatch from the magnetometers...

I also have built an Alpaca ASCOM controlled dew heater setup that uses the temperature of the scope and the domes central measurement of humidity/dewpoint to determine the amount of power to put into the heater band. Servos the value automatically. I won't claim its wonderful until more testing is complete but I hope so. M

I would try to model it as the balance between power injection and thermal radiation. The target being to keep the lump of glass in positive power budget to maintain its temperature above the dew point. For example, I put 5 watts in and assume it's all heating the OG. The OG is at 5 Celsius and has say an area of pi*100#2/4 ( ie 100mm diameter). We want to keep the OG above a level which represents the local dew point, say 5 Celsius or 280K The glass is radiating as a blackbody with temperature 280K into a void of temperature 245K (typical night sky apparent temp is about -30). The rate of radiation of energy is...... Which I make as 0.123 mW assuming an emissivity of 0.8. (http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c3) So, the rate of injection of heat required feels quite low. But losses into the tube probably means the amount of heat we can inject into the glass is a small fraction of the heat we provide. I'm not sure it's as low as 1/5000th though. Feel free to poke holes.this is a thought experiment on the train home. Mike

I have a qhy9 CCD camera. it comes with a little dessicant container that screws to a port on the outside. The first time out it froze on the coverslip of the ccd. And the second , and the third. So I bought some dessicant fabric from Browns and cut it to shape inside the CCD chamber, removing the tiny old dessicant strips. I also added the extra front window to the body which was meant to improve things. What I found out was that the without the 'extra' front window sealing the body, the front of the camera was open to the air and the dessicant wasn't actually doing anything useful since it wasn't connected to the ccd chamber. So I also revamped the dessicant - now I had a great big container of self-indicating dessicant attached, and a line to purge with argon and the front window attached to seal the body. I'd have thought that was enough. It looks enough compared to the few grammes of dessicant in the previous tube. Its a car petrol inline filter btw attached to gas line hose using quick lok gas fittings and valves. At this point I find the argon hissing out through the connector holes and through the body screw holes when I purge. So I sealed the screw holes with teflon washers I also sealed the connectors (usb 2 and 8-pin din power) on the inside with styrene resin , rolled about a touch to make sure it covered all the interior of the connectors. Then I re-purge with argon and find the front window isn't really sealed, you can feel the flow past the edge of the window when you get close. But it operates down to -20 reliably. and has done for about 3 months. Until tonight. when Voyager decides to take it down to -36, as it can do if the camera is disconnected and re-connected. Lord knows why. At that point I suspect the reduction in internal pressure due to the water freezing out pulls in more air from the outside. which should be being dried by the dessicant, but its still got a whale of ice on the front coverslip up past -5 and climbing. Its also got a heater on the coverskip . Well, that seems ineffective. the big silver thing is my homemade rotator slip ring. The green thing on the coverslip immediately surrounding the ccd detector areas is the resistor-heated anti-dew heater. Has anyone got a magic bullet for this or are they all this bad at dewing up and freezing ? Lovely clear night of imaging aborted while I warm it up, remove the camera from the scope, remove the dessicant pad, put it in the oven in a tin with other dessicant to reactivate, re-assemble, gas purge and then reconnect and re-align . FFS.!! Seething I am.

That earth is flat!

I have an. Off the shelf powerbank which came with a 19v output and recharges my laptop 2-3 times before flat. It's one of the ones that double as car starters. It's currently used to power my onstep for about 6 hours continuous alt az tracking. I agree with not going down the asiair route if you want flexibility and compatibility. It depends on how flexible you can be.

I read the docs re synchronising two sessions of as, does this mean it can effectively control 2 main cameras and one guide ? I've always wanted the ability to run more than 2 cameras together from one piece of software.

That needs some photos please.

Heating and tightening might help before going for the loosening.

No hope for all our camera optics with their silicone damping grease then. I used to use a silicone compound in industrial holography. No problem with coatings release or glass contamination there.