Questions regarding ATM

Hi!

I hope you don’t mind me asking two questions, regarding amateur
telescope making:



1. How... Ineffective or less “good” is a 6 incher from an 8 inch mirror?

[6 Inch with a F/8 ratio, or 8 inch with a F/6 ratio, hence focal length
isn’t significant].

I am aware that there will be an “effective magnification”

drop from 400x to 300x, but I am unsure as to how that may affect
planetary observing? [I know that aperture is more important, but is say,

240x with some knocked off cos of seeing enough?]

I know that brightness and light gathering will be less for DSO and
planets, but how significant is this? [I.e. 6 inch vs. 8 inch, how much
would I lose? Cos I was gonna make a 8'' but the cost seemed too high for

me, so how sufficient is a 6''? ]



I am also aware that light-gathering and brightness would be reduced in
the 6 inch, but for a first telescope making attempt, is a 6 inch, f/8
too small or insignificant for observing of the cosmos? [Would one be
able to see clouds on Jupiter [small, of course, not like Voyager! ] and

Saturn’s ring(s)]? N.B. I am aware that DSO won’t be in colour or like
pics in books etc. cos of the human retina etc., just wondering how a
planet would look like through a 6 incher].



2. Secondly, I have heard folks comment [and the FAQ!] that making one's
own mirror for cost isn't a good reason for small uns.

Well, I did some comparisons, and found a 6 incher mirror would
cost about £150 to buy, whilst to make it would cost:

£~75 [incl. p+p], including £23 for aluminising + p/p,

£23 for a mirror "kit" [pitch, grit etc.], and £33 for blank incl. p+p+,
roughly]



Well, putting aside labour costs, it seems there is a significant saving?

[If I made an 8 inch one, it would be £40 more tho.]

Have I missed something out significant here in the mirror making
stuff? I know that I'm missing the Tool, but would one be able to make
one cheaply at home?


Any advice would be much appreciated.



Thanks in advance.

#MK.

On Thu, 03 Jul 2003 16:20:17 GMT, in uk.sci.astronomy , #MK
wrote:

Hi!

I hope you don’t mind me asking two questions, regarding amateur
telescope making:



1. How... Ineffective or less “good” is a 6 incher from an 8 inch mirror?

the 8" will gather 64/36 times more light
any flaws in the grinding will be 64/36ths more noticeable.

[6 Inch with a F/8 ratio, or 8 inch with a F/6 ratio, hence focal length
isn’t significant].

the shorter focal length will show a little more aberration I believe.


--
Mark McIntyre
CLC FAQ http://www.eskimo.com/~scs/C-faq/top.html
CLC readme: http://www.angelfire.com/ms3/bchambless0/welcome_to_clc.html


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On Thu, 03 Jul 2003 16:20:17 GMT, in uk.sci.astronomy , #MK
wrote:

Hi!

I hope you don’t mind me asking two questions, regarding amateur
telescope making:



1. How... Ineffective or less “good” is a 6 incher from an 8 inch mirror?

the 8" will gather 64/36 times more light
any flaws in the grinding will be 64/36ths more noticeable.

[6 Inch with a F/8 ratio, or 8 inch with a F/6 ratio, hence focal length
isn’t significant].

the shorter focal length will show a little more aberration I believe.


--
Mark McIntyre
CLC FAQ http://www.eskimo.com/~scs/C-faq/top.html
CLC readme: http://www.angelfire.com/ms3/bchambless0/welcome_to_clc.html


----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeed.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =---

Where is a good place for looking into purchasing kits / elements for a
home made telescope?

I'm interested in building one myself (ex-student you see)

What is the general cost of building a telescope yourself?

Cheers

Kevin Jenner

In message , #MK
writes
Hi!

I hope you don’t mind me asking two questions, regarding amateur
telescope making:



1. How... Ineffective or less “good� is a 6 incher from an 8 inch mirror?

[6 Inch with a F/8 ratio, or 8 inch with a F/6 ratio, hence focal length
isn’t significant].

I am aware that there will be an “effective magnification�

drop from 400x to 300x, but I am unsure as to how that may affect
planetary observing? [I know that aperture is more important, but is say,

240x with some knocked off cos of seeing enough?]

I know that brightness and light gathering will be less for DSO and
planets, but how significant is this? [I.e. 6 inch vs. 8 inch, how much
would I lose? Cos I was gonna make a 8'' but the cost seemed too high for

me, so how sufficient is a 6''? ]



I am also aware that light-gathering and brightness would be reduced in
the 6 inch, but for a first telescope making attempt, is a 6 inch, f/8
too small or insignificant for observing of the cosmos? [Would one be
able to see clouds on Jupiter [small, of course, not like Voyager! ] and

Saturn’s ring(s)]? N.B. I am aware that DSO won’t be in colour or like
pics in books etc. cos of the human retina etc., just wondering how a
planet would look like through a 6 incher].



2. Secondly, I have heard folks comment [and the FAQ!] that making one's
own mirror for cost isn't a good reason for small uns.

Well, I did some comparisons, and found a 6 incher mirror would
cost about £150 to buy, whilst to make it would cost:

£~75 [incl. p+p], including £23 for aluminising + p/p,

£23 for a mirror "kit" [pitch, grit etc.], and £33 for blank incl. p+p+,
roughly]



Well, putting aside labour costs, it seems there is a significant saving?

[If I made an 8 inch one, it would be £40 more tho.]

Have I missed something out significant here in the mirror making
stuff? I know that I'm missing the Tool, but would one be able to make
one cheaply at home?


Any advice would be much appreciated.



Thanks in advance.

#MK.





--
Kevin Jenner

Where is a good place for looking into purchasing kits / elements for a
home made telescope?

I'm interested in building one myself (ex-student you see)

What is the general cost of building a telescope yourself?

Cheers

Kevin Jenner

In message , #MK
writes
Hi!

I hope you don’t mind me asking two questions, regarding amateur
telescope making:



1. How... Ineffective or less “good� is a 6 incher from an 8 inch mirror?

[6 Inch with a F/8 ratio, or 8 inch with a F/6 ratio, hence focal length
isn’t significant].

I am aware that there will be an “effective magnification�

drop from 400x to 300x, but I am unsure as to how that may affect
planetary observing? [I know that aperture is more important, but is say,

240x with some knocked off cos of seeing enough?]

I know that brightness and light gathering will be less for DSO and
planets, but how significant is this? [I.e. 6 inch vs. 8 inch, how much
would I lose? Cos I was gonna make a 8'' but the cost seemed too high for

me, so how sufficient is a 6''? ]



I am also aware that light-gathering and brightness would be reduced in
the 6 inch, but for a first telescope making attempt, is a 6 inch, f/8
too small or insignificant for observing of the cosmos? [Would one be
able to see clouds on Jupiter [small, of course, not like Voyager! ] and

Saturn’s ring(s)]? N.B. I am aware that DSO won’t be in colour or like
pics in books etc. cos of the human retina etc., just wondering how a
planet would look like through a 6 incher].



2. Secondly, I have heard folks comment [and the FAQ!] that making one's
own mirror for cost isn't a good reason for small uns.

Well, I did some comparisons, and found a 6 incher mirror would
cost about £150 to buy, whilst to make it would cost:

£~75 [incl. p+p], including £23 for aluminising + p/p,

£23 for a mirror "kit" [pitch, grit etc.], and £33 for blank incl. p+p+,
roughly]



Well, putting aside labour costs, it seems there is a significant saving?

[If I made an 8 inch one, it would be £40 more tho.]

Have I missed something out significant here in the mirror making
stuff? I know that I'm missing the Tool, but would one be able to make
one cheaply at home?


Any advice would be much appreciated.



Thanks in advance.

#MK.





--
Kevin Jenner

Kevin Jenner wrote:
Where is a good place for looking into purchasing kits / elements for a
home made telescope?

I'm interested in building one myself (ex-student you see)

What is the general cost of building a telescope yourself?


All the info you may need is linked to from:
http://astunit.com/tonkinsastro/atm/beginner.htm

Best,
Stephen

--
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books +
+ (N51.162 E0.995) | http://www.astunit.com +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

Kevin Jenner wrote:
Where is a good place for looking into purchasing kits / elements for a
home made telescope?

I'm interested in building one myself (ex-student you see)

What is the general cost of building a telescope yourself?


All the info you may need is linked to from:
http://astunit.com/tonkinsastro/atm/beginner.htm

Best,
Stephen

--
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books +
+ (N51.162 E0.995) | http://www.astunit.com +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

#MK wrote:
but would you happen to have a suggestion as to where I could obtain
primary for under 100 quid?

£89: http://www.scsastro.co.uk/it290004.htm
£109 (with flat):
http://www.galvoptics.fsnet.co.uk/te....htm#parabolic

Also monitor: http://www.ukastroads.co.uk

Best,
Stephen

--
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books +
+ (N51.162 E0.995) | http://www.astunit.com +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

#MK wrote:
but would you happen to have a suggestion as to where I could obtain
primary for under 100 quid?

£89: http://www.scsastro.co.uk/it290004.htm
£109 (with flat):
http://www.galvoptics.fsnet.co.uk/te....htm#parabolic

Also monitor: http://www.ukastroads.co.uk

Best,
Stephen

--
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books +
+ (N51.162 E0.995) | http://www.astunit.com +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

#MK wrote:
--- Cheap student, for whom time is not an issue, though cost is!

You want to go cheap? OK. Lots of things can be made very cheap or are
scroungeable.

Mirror-blank: Porthole glass (just make sure it's not hardened glass --
you will *never* get it to figure.

Sub-diameter tool for hogging out: Cat-food tin or similar, with
"rolled" end, full.

Tool for fine-grinding: cast plaster or cement base, with pieces of
bathroom tile epoxied on. Use a plaster base for your pitch lap.

Grits for hogging out and first stage of fine grinding: Sand. You will
need lots of it, but it's free. Grade it yourself.

I'd still advise buying finer powders, CeO and pitch.

Flat: prism from broken binoculars or similar, or bit of first-surface
mirror from photocopier. (CA isn't too bad if the scope is f/8 or above)

Timber for building scope and mount: scrounge from skips or building
sites. Or you can sometimes get offcuts of large-diameter tubing from
agricultural suppliers.

The junk corners of 2nd hand chandlers are a treasure trove of stuff for
broke ATMs (I was devastated when "Yot Grot" in Lymington closed down!).
So is Anchor Surplus in Nottingham (just next to Trent Bridge cricket
ground), although they seem to be getting wise to it and the prices are
going up.

Best,
Stephen

--
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books +
+ (N51.162 E0.995) | http://www.astunit.com +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +