Physopto

Aye Damian,

Give the flat blank to Mike.

Mike will probably bring it to me and he'll hold it while I use the grinder. Got a really good diamond plate to finish it off with and a bit Brasso.

"Simples" as the Meerkat would say!

Hi Derek

I normally leave the mirror about half an hour at this stage as I have that much materiality remove it doesn't make much difference.

In the later figuring stage (which still seems a long way off!) It will be a case of leaving it a lot longer possibly over night.

I don't have real a means of temperature control in my test area (the lounge) but keep the heating off as thermals distort the images

Hi Damian,

Pity you don't have a walk in fridge then. It would make the final figuring closer to the temp you will be using it at. .

Sorry just had to.........

Derek

Hi Damian,

How long after finishing the work on the glass do you allow for cooling before you take these images? Also do you keep the temperature in the room the same each time for the images and for the polishing?

Derek

I hope there is a long que to look through the scope when Damian is finished. Demon Barber and I have got our plans drawn up for the Big Dob Event at the Galloway Star Party. We are finalising the ticket sales! Rope lines are all planned. So Damian is well booked.

Derek

Hi Damian,

If you are pressing the lap now, does it not take on the shape of the hill in the middle? Or does that not matter as it is relatively small?

Derek

Aye Damian,

You can see the correlation between the two different methods showing the same centre hill. Very interesting. I'll keep watching.

I have just spent the last month and a half digging in the garden to remove an old pond plus about 70 square Metres of grass and replace it with new rolls of turf. As always it is the preparation that takes the time. But rushing either the preparation or the finishing straights can screw things up. So best of luck and be careful you will get there.

Derek

How long is a while ?

Don't answer it's just a rhetorical question.

It's a long job you've set yourself. I think if I had been doing it, by now ( actually a long time ago), I would have fixed up a washing machine motor and table for myself!

Hope you conquor the hill soon.

Derek

Damian,

When are you off to see John? Are you getting rid of the centre hill first?

Derek

Well just take your time Damian, I would hate to see you get so close then rush it when getting too excited close to  the finish line.

All the best

Derek

Well to my untrained eye they look as though the edge is reduced. Good to see.

Hiya Derek

I've been struggling this week for time on it and only managed 5hours of work on it last week.

I have more work planned this aft so will update with the progress images later today for definite

Damian

I like the way you say ONLY!!  That's a lot of work and every bit gets you that bit closer. I'll keep an eye out

Derek

Hi Damian,

I am getting withdrawal symptoms, how is the edge coming along. Any pics? No rush

Hope the weeks holiday set you up again for the work ahead.

Derek

Hello everyone,

 A while ago I posted a note about Optec and no response to emails. Then a follow up about actually getting in touch with them. It has taken up until today to get the final correct adapter from the USA. The final adapter arrived this morning 22nd May after being posted 15th May. It took 10 days to be made in the USA. Optec's Owner Jef Dickerman and his wife Tina were very pleasant and helpful to deal with. Unfortunately their communication skills are not quite so good at times. One of the first adapters that I received was incorrect, even though I had explained it carefully in the original email for the order. Their numbering system is complex  at times as not all parts are on their website nor are there pictures of all the parts. Never the less they tried to help me at all times. At first Jeff identified the incorrect part for adapter I needed, even though he had supplied the bit that was to screw onto it.

The part I needed, they did not have,but they pointed me at a web site called "PreciseParts ". So the correct part was eventually ordered by them from that firm. It was specially made for me, and is well worth a look if anyone is struggling to get an adapter over here. 

Although there have been several problems in the order I am happy with the items received. The rotator is very nicely made and would appear substantial.

The initial enquiry was made about the 15th March I think but no answer received.seems  very substantial. As soon as I get a chance to use it I will be a happy man (hopefully).

I initially emailed Optec about the  15th March, no answer.

1st April I did get an answer after a telephone call to the States.

Several emails back and forth order placed 3rd April.

Confirmation of order  being held by customs from FedEx 9th April.

Order delivered April 10/11th (unsure now).

Incorrect part found and emails again.

Incorrect part sent back to USA  cost £ 14.95 insured etc. 5th May received Optec 11th May.

Correct part received today and fitted.

Derek

There are possibly two methods that can be used to put out a fire without using water. (To not cause damage to equipment).

Halon and CO2.

Some years ago when at sea as an engineer we had Halon as the fire fighting extinguishing medium. At that time we were informed at the course we attended for these new ships, that Halon was completely safe. We were told that you could walk through an enginroom filled with it to check it had put out the fire.

So being a curious person I did a lot of checking upon Halon. At that time there was no internet!

It took several months to get the details about Halon. Yes it does put out fires. It is used at a concentration of about 4% in the atmosphere. This is because of cost and is the optimum for fire suppression.

But what had not been mentioned on the course was that Halon in the presence of flame produces Phosgene Gas, (Mustard Gas). At that time it was also not known that at concentrations above 4% that it was dangerous to humans even without any flame present. You can die as it is then a poison.

It has been mentioned here that the preferred method of fighting a fire in the observatory is CO2.

To extinguish a fire with CO2 you will need to flood the area with about 40% of its volume for CO2 to work. To accomplish this you must seal the area to contain the CO2 for several, and possibly even tens of minutes. This is to 1) extinguish the fire. 2) allow the item/s to cool so as not to reignite when air is allowed to re enter the area.

It will be very hard to seal an observatory before using CO2! By that time the fire will be beyond your control.

If a fire starts and you are there CO2 can be tried if it is caught before it has really got hold. BUT please just ring 999 and get proper help.

You only live once. Possessions can be replaced!

Derek

I use the sky x. I have starry nights also but don't like it much. It's just a personal choice I suppose. I tried carts du ciel but again not used to it so am sticking to what I'm happy with.

Derek

I see you are back on the grind again, OK polishing/figuring?

Keep it going Damian, missed all the drama!

Derek

A suggestion only!

If you are going to build a variable speed motorized table have a look at the way an old Myford lathe or a large pillar drill press works. Just use pulleys and a slow 4 pole motor ( 1500 rpm). Easy to change speeds and reliable. Just over size the motor and any bearings used if possible. MDF can always be glued and screwed together to increase thickness to anything wanted. But it is not the best product for use near water regardless of what protection used.

Derek

OK James,

I was hoping it was something simple/daft.  I really liked mine. After the bearing problem was realised, it was rock solid. Probably one of the best upgrades I did.

Best of luck.

 Derek

James,

Are you sure that it is not the bearing not being centred. I had the

At problem at first. The roller bearing was not properly centred when Input it together the first time which allowed the movement.

Derek

Now you've done it grass, oh sod it!

Derek

Well you go from a high to a low. Been waiting for a camera rotator arriving from the States. Arrived today and guess what: wrong threaded end. They sent a male 92x1 mm fitting instead of a female. Partly my fault and partly theirs. So awaiting a reply to my email now to see what can be done, as I cannot find the correct bit on their site. You win some and loose some

How's that edge doing?

Derek

Hi Damian,

 You talk about taking time to do the mirror! well last night I just managed to get my Active Optics to work after nearly 14 months. Spent 5 hours last night with it. 3 hours in vain then Eureka Ta Daaaa! 2 hours of perfect guiding within 0.2 pixels, wow!

Mirrors PA PISH POSH.

Keep going, you'll get there.

Derek

Hi Damian,

I wondered about that, (the lump in the middle and shape on the pressing). Hope it works for you. I know when things are not going to plan it can get demoralising to say the least. When it happens to me on anything,  I just tend to get angry with myself, becoming more centred and stubborn, I hate giving up.

As I said I tried two instances of I.E. open with different pictures of your tests in view, the effect is difficult to see for an untrained eye.

Thanks for the updates and explanation. I went off to Utube for  a search about chordal strokes. So got it now.

Best of luck Damian.

 Derek

Thanks John.

What is chordal ?

Derek