Building a new tailgate

[Doogs38 (Alex)]

G'day :-) Here in SEQLD during winter, the air's cooling gradient becomes quite steep once the sun goes down. After I put a temp sensor on my (Skywatcher conical) 14" primary I learnt that my mirror has no chance of matching the rate of temp drop (which explains nicely why my planetary views are crap atm!). I cannot install any fans to help the mirror cool due to: a) the unique Skywatcher conical mirror mount; and b) the extant tailgate on my dob is solid, thick plywood Soooooo, I'm making a new tailgate but one that's more like the 'standard' Obsession style metal frame, although, my conical mirror mount makes it look a bit different! There's probably a dozen different ways to achieve the same outcome but this one will do for now. I'll be finishing it this week, and hopefully, trialling it next weekend with two or three fans installed. I've attached images of the basic design, welding jig, finished (very) raw tailgate and current tailgate. Fingers crossed Alex

[Doogs38 (Alex)]

My new, (very) open tailgate is progressing well. Completed all the drilling and refinement of holes today, made some new springs (that I'm not happy with), and mounted the mirror for a test tonight. I breathed a huge sigh of relief when my dob collimated well and focused well too. It's clear that the mirror's centre point relative to the mirror box has moved a little bit, and I had to fuss for a while with the collimation. However, I would say that mirror's centre point is now where it should be as the wooden tailgate appeared to mount the mirror ever so slightly off centre, as evidenced by a difference in the location of collimation bolt holes between the metal and wooden tailgate. The metal tailgate weighs only approx 500g more than the wooden tailgate, so I still need a counterweight on the mirror box - bugger

Now I need to clean up the metal work, prime and paint it, and start using it!

[ZeroID (Brent)]

Wow ! Very minimalist for sure. Nice work, obviously makes a difference.

[Doogs38 (Alex)]

Thanks Brent. It is minimalistic, isn't it! But I like it :-) It took me only two weeks to go from frustration, to an idea, to having a new tailgate. I've got it to the 99% mark - it looks even better now that it's cleaned up and painted. Everything about the new tailgate has improved my dob: improved cooling potential now that the back is open; the collimation 'picture' in the eyepiece looks better now that the mirror is truly centred; the collimation springs are superior (longer and stiffer); I've removed the poorly performing collimation locking plate and bolts; and, it makes the dob look great! I just wish the clouds would p#$$ off so I could use it