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Topics - monsresiwor

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1
ATM, Optics and DIY Forum / Strange PLOP result
« on: December 31, 2017, 05:53:18 AM »
Hi:

I have been playing with PLOP, looking for a better cell for my telescope. I'm trying to find a good solution not on only for the case with the the telescope pointing to zenith, but also for the telescope pointing to some realistic altitude.

For do this, i used PLOP to calculate the "Z88 RMS Error" for different mirror tilt angles. I did this for various designs and i made a plot for the "Z88 RMS Error"/angle values. I followed some indications from this page: http://www.skyinspec....uk/use-of-plop

For this design (18 points cell):

I obtained this result:

Where the tilt angle is represented in the horizontal axis and the correspondent RMS error in the vertical one.

This result seems reasonable and is how i expected: for major tilt, major RMS error.

But I had a big surprise when i repeated the experiment for 9 and 6 points cells.

For 9 points i obtained:



And for 6 points:



As you can see, in both cases the RMS error is less for a major mirror tilt!!!!

This is a very surprising result for me. I think it is very logical....

To be honest, I think that I must be making a mistake... but i don't find it... very frustrating.

Anyone have idea about a plausible explanation for this strange behavior???

The used mirror parameters:
Diameter: 30mm
Thickness: 37mm
Focal length: 1500mm
Diameter of the secondary mirror: 70mm
Material: Plate glass
Sling included angle: 180

Best regards.

2
I have two issues on my scope and I wonder if they are related. For reference, this is the TS ONTC 8" f/4 newt with a 2.5" Moonlite focuser.

1) My secondary isn't centered under my focuser (or at least I assume so). My flats show that the center of illumination is offset towards the right-hand side of the frame (towards the primary mirror). I assume that my secondary needs to be pulled in towards the spider. I've been ignoring this issue since I thought I read that the only negative of an un-centered secondary is the uneven illumination. Flats take care of it, so I assume it's a non-issue.

2) Tilt issues on my focuser/camera. To get a somewhat flat field, I need to adjust the focuser tilt adjustment screws about 1/8" up in the front of the scope. This tilts the focuser aim away from the primary by a degree or so, which is quite a lot for what should be a very rigid and square OTA.

I have a tough time thinking that my optics or tube are this far out of alignment, so is the tilt requirement related to the secondary positioning? If I spend time squaring the secondary up will I be able to reduce my focuser tilt?

Something else that is odd/interesting, the darker corners on my flats are the same corners that give me star quality issues that require me to adjust my tilt.

Thanks,
Phil

3
Reflectors Telescopes Forum / Thinking of selling...
« on: December 29, 2017, 03:32:07 AM »
SO I'm trying to make up my mind about selling my very old homebuilt GEM Newtonian. It's a Meade 10" f/4.5 mirror refigured by OWL coatings in Sacramento. They did a nice job although the mirror still has a ding in the middle where a secondary crashed into it. It has a MoonLite crayford focuser and a Protostar BlackLight tube. The mounting has a 1.5" RA shaft and a 1" Dec shaft with Opticraft drives on both axes. I have a 12v to 110v Drive corrector. The Pedestal was made by me as with most of the mounting. It's pretty solid. Eyepieces include University Optics Orthos (24mm and 10.5mm, 1.25"), a 30mm Meade 2", a University Optics 15mm Ortho 2". I've also got some filters including a 2" variable density and a 1.25" variable density. There is also a 70mm Finder scope and the usual odds and ends.

Why am I thinking of selling? Our neighborhood is crime-ridden and everyone is turning on their outside lights and we have constant patrols by police and neighborhood watch going up and down the street. It's crazy and we're still getting broke into, vandalized and so forth by the constant stream of homeless and drug addicts. Very depressing. To transport the telescope is no mean feat. I have to fold down the seats of my Prius to get everything in there. My goal in building the scope was to start taking photos. To do that I have to get out of the town, but I'm the care giver to my son who has cystic fibrosis so I have to keep an eye on him at night when he's sleeping. I have no idea what a full night of sleep is.

To sum up, I have about $2000 into the building of this scope. I know I won't get anywhere near that amount. We have almost no astronomy hobbyists in the area and those that are have computer-aided scopes. I have thought about parting everything out, but I'm not looking forward to spending years trying to find homes for all the pieces of this thing.

So I would love to have some input...... Thank you!Attached Thumbnails

4
Beginners Forum / Only see Support bars of 2nd mirror thru reflector scope
« on: December 28, 2017, 03:32:46 AM »
I tried to search this problem but didn't find my answer.

I am using a Cassini 1000 x 120 reflector.

Examples = looking at Jupiter and Venus

When I use a 23mm eyepiece, I see just large dot, slightly larger than the naked eye, when I scroll to focus or if I use a 10mm Plossi, all I can see is the light and the crossbar supports at the secondary mirror,
With 10mm, if I focus down to remove the crossbars, all I see is the same dot of the planet.

Anyone know what I am doing wrong and what do I need to do?

Larry

5
Eyepieces Questions & Recommendations / Repair damaged Baader zoom.
« on: December 28, 2017, 12:23:27 AM »
I dropped a baader zoom a few weeks back, and now the zoom mechanism is stuck between the 8 and 12mm settings. I've tried moving it by force, but it will not move at all. Has anyone had this issue before and successfully repaired one. It's a mark lll model.

6
ATM, Optics and DIY Forum / Winspot source code availability?
« on: December 27, 2017, 08:45:57 PM »
Unfortunately, it appears that http://bhs.broo.k12....lot/winspot.htm is no longer in existence.

I have a copy of the executable, Winspot_0.95d.zip, but am looking for a copy of the source code, i.e., WinspotSrc_0.95d.zip

So far both Google and the Wayback Machine web.archive.org have failed me. Does anyone here know how to find a copy of the source code.

I do have and am using the educational copy of OSOLO EDU which is very nice but I have found Winspot to have its uses also.

7
ATM, Optics and DIY Forum / Public Telescope build
« on: December 24, 2017, 07:56:20 PM »
Ok, so I've done some thinking about this.  If there's one in which you may do this I want to know butotherwise please notice me with this.  So I have been considering creating a public telescope available to everyone across the world through the net.  The telescope observatory would be of a modest diameter of about 40-50"  so that it could be able to see just about any kind of DSO or planetary thing.  The person or group of people would be able to purchase telescope time in as big of an increment as they'd like.  They could buy out the entire night if they'd like.  The person/s would be able to point the scope at anything over the horizon.  Now I think I have the property that will suit the observatory through a family member, all we want are strategies and then from there go onto resource and money acquisition through Kickstarter or a different crowdfunding website.  We'd provide different amounts of a membership for after a week and so forth.  If anybody else has any modifications or ideas they'd like to include please throw your piece in!  This is just an idea now and has nothing behind it but a mind that want to see this occur!

8
ATM, Optics and DIY Forum / Looking for opinions. twelve inch F6.0 or F7.0?
« on: December 24, 2017, 05:42:05 PM »
Hello everyone,
I've started rough milling my twelve inch mirror blank.  I'm doing all of the work by hand as I don't own a machine.

Originally I wanted to make an F5.0 mirror, and I had rough floor the mirror into a sagitta depth of 0.150".
I recently changed my mind and thought I would rework the mirror to make it an F6.0 mirror.
Currently, while grinding for a couple of hours, rather than having much to occupy my thoughts other than count 1, 2, 3, 4, 5, 6....  I began to consider making it an F7.0.
I believe the only downside to the F7.0 is that the whole telescope assembly would be rather long and cumbersome to carry.
Maybe it would also be more challenging to balance?  Or collimate?

Anyway I decided I would reach out to everybody and solicit some feedback.
This is a twelve inch plate glass mirror.  It is 3/4 of a inch thick.
By what I have read, a shorter focal length mirror is harder than a more focus mirror.
I had a ton of fun making the ten inch mirror and I had a great deal of advice from several people in this forum.

Is this really a half one and a half a dozen of the other kind of question?

One final note.  I love the 12" mirror.  Focal Length is sooo easy to determine :--RRB-

Thanks

....Cameron

9
General Astronomy & Observing / Anyone using a drone to photograph eclipse?
« on: December 24, 2017, 02:47:33 AM »
Some time back I had been considering the purchase of a GoPro or any other broad field camera to photograph a broad scene at this year's eclipse when the thought occurred to me, "Why not use a drone".
Is anybody planning on doing this?  If so where?
It would be great if there were a range of them throughout the path of totality for live streaming.
Perhaps a drone flown high enough might be able to capture the shadow as it arrives.
Seems like an exciting chance.

10
Beginners Forum / Would you recommend a Celestron Luminos EP?
« on: December 24, 2017, 01:40:37 AM »
My 16th birthday is next month and I started searching for an eyepiece.  My budget is $160 but I intend on renewing my S&T journal subscription which brings my EP budget to around $120.  I'm trying to find a high or medium power eyepiece.  My top alternative is that the Celestron Luminos series for under $100.  How good are they?  I understand they have an 82?? afov which is actually wonderful.  If they are good, I do not know whether I need to get the 7, 10, or even 15mm.  Another eyepiece I'm contemplating is a zoom EP which would cover my requirements but would not be too much of an excellent upgrade.  When I purchase the Luminos, I've a 3x barlow which would go on my own 32mm plossl for medium power or the Luminos for high power based on which model I purchase.  How good are the Luminos eyepieces and what would you do in my situation?  Are there any other eyepieces that I need to consider?  My gear is in my touch, thank you

11
Beginners Forum / Eyepieces for 8" DOB
« on: December 24, 2017, 12:12:54 AM »
Hi,

I have recently purchased a brand new 8" DOB.  It came with two eyepieces, 25 mm and 9 mm.

Will it be useful to have a 40 mm eye piece like I am hoping to get a wide perspective with it.  When seeing objects like 'Pleiades' with a 25 mm eyepiece, it doesn't pay for the complete set.  Will the 40 mm offer better views?  I am OK with low magnification if the quality is greater.

Aniket

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