Orion Optics VX12 1/10pv

[jetstream]

20 hours ago, Paul73 said:

The two sets of figures don't seem to tie up. Could be that we are comparing apples with oranges. Couldn't say which are correct.

But, either way, it looks like you have got a great mirror there. 

Paul

PS. It was the wicked queen who had the mirror......

 

Hi Paul, it means Dereks mirror is higher than Royces averages.... P-V is interesting but the RMS and Strehl tell the story IMHO.

[jam1e1]

Looks good! did yours come with an adapter of any sort to connect to the fan?! ive not got anything hence may have to potentially fabricate something from maplins!

[DRT]

2 hours ago, jam1e1 said:

Looks good! did yours come with an adapter of any sort to connect to the fan?! ive not got anything hence may have to potentially fabricate something from maplins!

No adapter. I had a quick look and it seems to be a standard jack plug but haven't seen (or looked for) and power rating. Not sure I really need it as I don't keep my scopes in the house so they are always around ambient temperature.

[DRT]

6 hours ago, jetstream said:

Derek you should be jumping up and down with excitement!!

These are excellent numbers and with them comes the assurance of a very smooth mirror...

RMS .016, Strehl .990 those are freakin' great numbers! you will have a very good MTF with this telescope..... Congrats Derek, Gerry

Thanks, Gerry, that sounds very positive.

I think I have gotten my head around PV and Strehl from reading various articles on the internet but am still baffled by what "RMS" (Root Mean Square?) is measuring and what good and bad readings look like. Are you able to give a layman's description please?

[jetstream]

"RMS wavefront: Root mean square error, or a statistically averaged error: The RMS is computed by finding the wavefront error at a bunch of uniformly spaced points on the mirror, computing the average error, then difference each individual value from the average, square each difference, sum the squares and divide the sum by the number of data points minus 1, and then take the square root. (If you're familiar with statistics, it's the same equation as for a sample standard deviation.) Because RMS says something about many points on a mirror, it is a much more meaningful measurement than peak to valley."

Low RMS is a good thing- it is just a single number derived from many wavefront readings across the mirror and then ^^ thats done with the numbers. It is one of many tests that prove a mirrors quality.

My VX10 tests @ .123 pv, rms .018, Strehl .986 and this mirror has very high contrast and supports high mag in good seeing. So will yours

[DRT]

Thanks, Gerry

 

[Moonshane]

Very nice Derek. I use an additional ring to prevent the tube sliding down. That said, Once I got the balance right, I have never really adjusted it again. I set it for my average eyepiece weight with finder/paracorr and add a little box of pennies at the primary end if required for my heavy eyepieces (just one these days). I just tuck it in the tube end near the cell with the weight at the bottom - also prevents the auto-raising at the zenith with heavy eyepieces.

[faulksy]

Nice one Derek.

Just to settle you, my 00  14" had 1/10 mirror and. 996 ish and would hold up to 500x on planets with great detail and on poor nights still around 300x hence the 20" with 1/10 

[DRT]

6 hours ago, Moonshane said:

Very nice Derek. I use an additional ring to prevent the tube sliding down. That said, Once I got the balance right, I have never really adjusted it again. I set it for my average eyepiece weight with finder/paracorr and add a little box of pennies at the primary end if required for my heavy eyepieces (just one these days). I just tuck it in the tube end near the cell with the weight at the bottom - also prevents the auto-raising at the zenith with heavy eyepieces.

I bought two extra rings with scope to use with my AZ-EQ6 so have fitted those outside the Dob rings and tightened them using a spanner, which seems to have done the trick. I also bought the friction brake for the Dob base so that should help with the balance issues.

I've just spent a few minutes collimating it, which was very straightforward, and it is now ready to go. So it has started raining

[Timebandit]

 ? .  Hi DRT sorry but I had to have a smile when you said it's just starting raining, that's typical when you get new kit. Your ready to go and the rain or clouds come in. Glad you got the friction brake on your dob very handy and IMO it's needed on these OO dobs.                                                                                                                                              I bet you have got itchy feet just waiting to get your new scope out and check the 1/10 mirror performance. I will keep my fingers crossed for you and that you get some clear skys later to see some of those bright sparkly things in the sky's. Good luck?

[nicoscy]

Derek,

I have the exact same scope as you with the same mirror configuration and similar figure. Stop worrying about Strehl and RMS and Wavefront. Get out there and enjoy the scope.

You DO need to get the fan running as the scope needs about 30 minutes cooling to give its best. I attach my observing list for last Friday and Saturday. I had a blast with the scope!

Weekend 8.7 - 9.7.pdf

[Timebandit]

39 minutes ago, nicoscy said:

Derek,

I have the exact same scope as you with the same mirror configuration and similar figure. Stop worrying about Strehl and RMS and Wavefront. Get out there and enjoy the scope.

You DO need to get the fan running as the scope needs about 30 minutes cooling to give its best. I attach my observing list for last Friday and Saturday. I had a blast with the scope!

Weekend 8.7 - 9.7.pdf

Hello 

I think one of the prime reasons people opt for a OO uk scope is because of the mirrors and the options of PV available (Streak and RMS). So it is IMO interesting to know what and how these figures mean. But most of all you know by having a quality mirror like 1/10 that you have a piece of equipment that is going to give you the best possible views subject to eyepieces and seeing conditions. A once in a lifetime purchase for many so it's nice to know about the facts and figures 

I never have used my fan to date in my OO uk as I have felt it has not needed it. The scope is kept outside in its own little shed(seems happy enough) . I suppose it depends where you keep the scope if you really need the fan to try to adjust the a temperature inside the tube/ mirror assembly to get it in line with the ambient temperature of the outside conditions. 

But then again Nicos if I was Lucky enough to live in the temperature's of Cyprus then I would need a fan ? 

[DRT]

1 hour ago, nicoscy said:

Stop worrying about Strehl and RMS and Wavefront. Get out there and enjoy the scope.

Easy said, but I have had one night of clear observation in six weeks due to our rubbish weather and northerly location which means it doesn't get dark until after midnight, and then only for about an hour. Fear not, as soon as I can get out there under the stars I will, but in the meantime it has been interesting to learn from others about what these facts and figures mean

I'm not convinced I need a fan. The scope lives in a shed, not in the house, and will not need to cool down.

[CraigT82]

32 minutes ago, DRT said:

Easy said, but I have had one night of clear observation in six weeks due to our rubbish weather and northerly location which means it doesn't get dark until after midnight, and then only for about an hour. Fear not, as soon as I can get out there under the stars I will, but in the meantime it has been interesting to learn from others about what these facts and figures mean

I'm not convinced I need a fan. The scope lives in a shed, not in the house, and will not need to cool down.

You may need it to help the mirror keep up with rapidly falling night time temps (in winter anyway).  Will also help to break up the boundary layer which sits just in from of the mirror as long as there is room for the passage of air from the rear of the cell to the front of the mirror? It's fitted anyway so I'm sure you can try it for yourself to see if it makes any difference on the next clear night (whenever that may be!).

On my 8" the stellar images were noticeably improved after fitment of a fan, which sucks air down the tube and out the back rather than blowing up. I think this is more to do with breaking up the boundary layer rather than cooling the mirror.

[DRT]

Thanks, Craig - I will certainly be giving it a go.

[Timebandit]

Hi, to fan or not to fan?  I was of the understanding that if the scope tube air/mirror assembly was at the ambient temperature already then by using the fan then there is really no noticeable benefit. 

And a fan to draw air in to the tube rather than push it up the tube nowerdays seems to be a more positive way of adjustment to your tube/mirror to ambient temperatures.   I would of thought unless there is a dramatic sudden change in temperature (when I can see that a fan would assist in bringing tube air temperature/mirror temperature more in line with ambient temperature then under normal temperature changes when observing then the fan going would not bring much benefit. Actually I think I read an article somewhere about fans that basically said a fan can be more of a hindrance when observing due to it disturbing air currents in the telescope tube that can effect the view through the eyepiece. I suppose if you think about it disturbing air currents in the tube is a bit like atmosphere disturbance which can be detrimental at times. But i am sure there are various options of thought on this.

By the way Derek ,now I have itchy feet also?. Had a parcel this morning containing some Pentax XW(  thanks Shaun) but the clouds are like a white blanket here presently so we are both in the same boat wanting to test our new purchases out?. 

 

 

[John]

I have a fan fitted to my OO 12" F/5.3 but I've never used it, in any season. I pop the scope out to cool for 20 mins or so, start on some low to medium power stuff and then start using higher powers after 40 mins or so. My scope lives in the corner of our dining room.

It's such an easy scope to use

[nightfisher]

Really looking forward to your first couple of reports on this new canon

[DRT]

44 minutes ago, nightfisher said:

Really looking forward to your first couple of reports on this new canon

It is out on the patio waiting on darkness falling. I had a quick focus test on the Moon and all looked well, although it was in full sunshine so not enough contrast to really count as fist light.

I will hopefully return later with some positive news!

 

[faulksy]

On 12/07/2016 at 14:03, Timebandit said:

Hi, to fan or not to fan?  I was of the understanding that if the scope tube air/mirror assembly was at the ambient temperature already then by using the fan then there is really no noticeable benefit. 

And a fan to draw air in to the tube rather than push it up the tube nowerdays seems to be a more positive way of adjustment to your tube/mirror to ambient temperatures.   I would of thought unless there is a dramatic sudden change in temperature (when I can see that a fan would assist in bringing tube air temperature/mirror temperature more in line with ambient temperature then under normal temperature changes when observing then the fan going would not bring much benefit. Actually I think I read an article somewhere about fans that basically said a fan can be more of a hindrance when observing due to it disturbing air currents in the telescope tube that can effect the view through the eyepiece. I suppose if you think about it disturbing air currents in the tube is a bit like atmosphere disturbance which can be detrimental at times. But i am sure there are various options of thought on this.

By the way Derek ,now I have itchy feet also?. Had a parcel this morning containing some Pentax XW(  thanks Shaun) but the clouds are like a white blanket here presently so we are both in the same boat wanting to test our new purchases out?. 

 

 

ill buy them of you, then the clouds will go away

[jam1e1]

managed to have a very brief session with mine last week (OO12 pv1/10)- had a go around cygnus, stuck with 17mm as seeing wasn't great and wasn't very dark - felt it showed a nice colour depth to stars, slightly more subtle than the 250pds. had brief look at planets but atmosphere really didnt help so will have to wait to next clear session to give a proper run - early results are pleased  

I have noticed similar issue with scope rings and slip - which ones did you upgrade to? J

[DRT]

17 minutes ago, jam1e1 said:

I have noticed similar issue with scope rings and slip - which ones did you upgrade to? J

I didn't upgrade them, I have just resorted to using a spanner to get a bit more tension into them than is possible with fingers alone.

[DRT]

10 hours ago, DRT said:

It is out on the patio waiting on darkness falling. I had a quick focus test on the Moon and all looked well, although it was in full sunshine so not enough contrast to really count as fist light.

I will hopefully return later with some positive news!

 

I stayed up until after midnight last night but the sky never got truly dark. Only the brightest stars and parts of the main constellations were visible to the naked eye so finding things was near impossible. I decided to just spend half an hour peering through the E21 and panning around the sky looking for anything interesting. Given the very small number of naked eye stars visible I was quite surprised by the sheer volume of stars visible through the eyepiece. The Paracorr 2 worked beautifully with pinpoint stars across the entire 100 degree FOV. The focuser on the VX12 is a good piece of kit with very positive and smooth movement. My only complaint is the very short draw tube (30mm movement) which necessitates the use of some sort of extension tube. I used the long nose of the Paracorr to serve that purpose, which worked very well. I stumbled across a number of lovely clusters and star fields but have no idea what they were. With no sign of true darkness falling and lots of thin high clouds beginning to gather I packed up shortly after midnight.

Not an ideal first light, but first light it was

 

[nicoscy]

Congrats on first light (and yes, it does count)!

I do the same thing with my Paracorr. I find that I need to pull it out by maybe 3 centimeters to have sufficient in and out travel with the focuser for my eyepieces.

The main thing I take from your post is that the telescope mechanics and built are just fine, no issues present with collimation, optics were on par to what you should expect and you need darker skies 

[DRT]

50 minutes ago, nicoscy said:

Congrats on first light (and yes, it does count)!

I do the same thing with my Paracorr. I find that I need to pull it out by maybe 3 centimeters to have sufficient in and out travel with the focuser for my eyepieces.

The main thing I take from your post is that the telescope mechanics and built are just fine, no issues present with collimation, optics were on par to what you should expect and you need darker skies 

That is a very good summary, Nicos