). La reflex es una Canon 300D que le he comprado a un amiguete de 2ª mano. Preguntaba esto ya que quiero empezar a investigar este campo, aunque paso a paso. Primero empezaré con el piggy back que recomendaba nandolorroco en un hilo que leí a otro compañero que también se iniciaba Me han ayudado mucho las fotos ya que nunca había visto esos adaptadores, por cierto, se parecen a un telextender, ¿es lo mismo?. Lo digo porque me variará en proyección ocular la distancia focal, ¿es correcto?.
y he pedido una anilla T2 para adaptar la Canon EOS 300D al LX90. Mi sorpresa ha sido cuando he llegado a casa y he comprobado los pasos de rosca. No coinciden. Veo que la anilla T tiene unos pequeños tornillos en los laterales, ¿quitando estos tiene un paso de rosaca mayor?¿necesito otro adaptador distinto?.
Subject: Thread Specs for Misc. Telescopes & Accessories
(http://www.mapug.com/AstroDesigns/MAPUG ... tm#threads)
From: Roger Hamlett <ttelmahntlworld.com>
This is a list, of some threads used in telescopes and accessories. Some are 'from specifications', while others have been taken from measurements. There are also some notes about 'oddities', with some parts, and in a few cases other data covering such things as the design 'focal plane' distance. If you have additional specs or corrrections, please contact me.
Meade:
Rear Port on 10" and larger models (excluding the C16) 3.25" * 16TPI
2" SCT 2" * 24TPI
ETX Rear Port 1.375" * 24TPI
This is to me, an 'oddity', since in general Meade threads are imperial, but the external measurement, seems to be fractionally 'oversize', and the thread is really closer to 35mm OD.
Celestron:
Rear port on C11 C14 etc. 3.3 * 16TPI
Many of the scopes outside diameters, measure slightly 'small', at about 3.29", but cutting to 3.3 for the outside of the thread teeth, gives a good fit, with reasonable clearance.
The rear cell on the smaller scopes, and on the rear of the adapter attached to the larger scopes, is the 2" SCT thread above.
On the 1.25" 'visual back', the external thread, is:1.38" * 24TPI
This is very close to the thread on the ETX, but is very slightly larger. The relationship of these two threads, is definately an 'oddity'. In most cases, accesories for each, will fit the other, provided they are slightly 'oversized' on the Meade fitting...
General:
M42/Pentax. 42mm * 1mm
This is the thread on the older StarLight camera noses, and on quite a few odd accessories.
The focal plane, is meant to be at 45.46mm from the camera face (45.5mm to the _rear_ of the film on a normal camera 'body').
T42 42mm * 0.75mm
This is the thread on the extension tubes supplied by Meade/Celestron, for their focal reducers, on the rear of some OAG's, and on a lot of camera attachments. The newer Starlight SVX-H9 family have this thread.
This is the thread normally called simply the 'T' thread. Beware though, that a lot of accessories that refer to a 'T' coupling, may use the alternative 'T bayonet', so make sure you are dealing with 'T-threaded' accessories when buying parts...
CS 1" * 32TPI
This is the thread found on some WebCams, and on the Starlight guide camera for the SVX. The focal plane, is meant to be at 12.5mm from the face.
C 1" * 32TPI
Identical to the 'CS', but with the focal plane at 0.69" from the nose (17.526mm).
The commonest 'webcam' lens thread, is 12mm*0.5
Filters:
1.25" eyepieces. These take filters measuring 28.4 * 0.6mm
This is another 'oddity'. Technically, there is a standard for camera filters, which are 99%, in 1mm (or occasionally in 0.5mm) steps, with pitches of 0.6mm, 0.75mm, and 1mm, according to size. The version used on telescopes, is (I believe), an imperial 'conversion', which has been modified to bring it 'in line' with the filter standard. I suspect the 'orginal', was: 1.125" * 42TPI.
There are a couple of old 'Leica' filters, which show this same 'between the steps' sizing.
Occasionally, some old filters turn up, which are very 'tight' in the modern threads (the imperial measurement, is 0.007" larger).
2" eyepieces. 48mm * 0.6mm
Again there is an 'oddity' here. Generally, on threads, the 'bore' is cut to the specified size, and the thread to fit inside is made a few thousands of an inch 'small', to give a comfortable fit. Some Meade 48mm filters, seem to be made with this thread slightly 'oversized', making them unconfortably tight (to the point where in some cases they won't fit...), in some other makes of eyepiece. Beware....
Others:
Takahashi, use an assortment of 'unusual' threads. So their eyepiece extension tubes, use 43mm * 0.75mm. The 'Rear Port' , on their scopes, is normally 72mm * 1mm.
Borg use a similar (even larger!), assortment of threads, offering adapters to many other makes, as well as their own variants. Fortunately, they publish a good list of the threads available, at:
<http://www.sciencecenter.net/hutech/techdocs.htm>
The 'component catalogue', gives the thread sizes for each end of the adapters in their range of products, including, the thread sizes used to fit many other makes of scope (Takahashi, Televue, Vixen etc,). This is therefore a 'gold mine' for anybody wanting to make adapters.
'Base' threads & Camera tripod:
1/4 * 20TPI. This is the thread in the side of an SBIG camera, and also in the base of ETX scopes.
5/16 * 18TPI. This is the thread in the top of most Meade/Celestron tripods.
3/8 * 16TPI. This is the thread into the base of several scope (the LX200, and the Celestron C11 for instance).
1/2 * 13TPI. This is the _centre bolt_, on the LX200 models.
Generally, all the imperial bolts are 'UNC' tooth form (60 degree). The metric threads are also this shape.
) . Para el C150N me vale tal cual, pero para el LX90 compraré el adaptador T que indicas.
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