ALPO Gallery Submission Guidelines for Comets

January 27, 2023

As noted by Tim Robertson in his introduction to the ALPO training program, “The ALPO revolves around the submission of astronomical observations of members for the purposes of scientific research.” To that end, we have guidelines for including observers’ sketches and images in the ALPO galleries that help ensure the material useful to scientific endeavors. Note: The following guidelines apply to observations submitted for comets; other sections have their own requirements.

File Naming Guidelines

The files that are sent to ALPO for inclusion in the galleries should follow a few basic rules to help ensure their indexing[i] and upload in a timely manner. Files should be attached, not embedded, with the email sent to The preferred naming is as follows:


  1. Start the file name with the comet name.
    1. For long-period and newly discovered short-period comets, this can be the comet’s full designation (e.g., C2020 P1 (NEOWISE)) without spaces or slashes. Alternatively, you can use just the comet’s ID (e.g., 2020P1)
    2. For numbered short-period comets, this can be the comet’s numbered designation with or without its name (e.g., 96P or 96PMachholz)
  2. The date and time of the observation expressed in UT
    1. 4-digit year <hyphen> 2-digit month <hyphen> 2-digit day 2022-03-29
    2. <hyphen> 2-digit fractional day -21
  3. Your initials in some manner, preceded by a hyphen -ChrsHrdr
  4. Any filter used -Lum
    1. If no filter, Lum is appropriate for “Luminance”
    2. If you created a color image by taking red, green, and blue images that are combined to a final product or used a OSC camera, then RGB is the correct value to use
    3. If multiple filters are used list them with intervening hyphens

If for some reason you must use a non-ISO 8601 standard for your UT date (i.e., something other than YYYY-MM-DD) then we require two things:

  1. It must be numeric; do NOT list a month using alpha characters such as SEP or APRIL
  2. You must be consistent, using that format for all your observations, regardless of target

Acceptable File Type

Only static JPG and PNG image files are accepted for processing. You can find free, online resources to convert almost any other format to either of these accepted types (e.g.,

Due to the large size of animated GIF files, we are currently unable to host these on the website. We hope to be able to handle them in the near future.

Maximum File Size

Because disk space on a web server is not free, we must cap the file size at approximately 300 KB. The compression algorithms for JPG files are very effective and can produce excellent results with negligible loss of detail. Files exceeding this threshold will be automatically resized to meet the limitation.

Image Annotation

Your image should have text annotation on it to assist anyone who is subsequently examining it to facilitate understanding what was observed and how it was captured. While some of this information is also present in the file name, having it visible on the image helps to ensure its permanent association with your observation (file names could change). Other important information would include:

Many observers include additional details like those listed below. As a general rule, the more information you document on the image, the more valuable it can be.

Email Address

Your observations should always be sent to to ensure that they are forwarded to the appropriate section coordinators and volunteers who prepare them for the gallery. 


The guidelines above not only help relieve the burden on volunteer staff who process the many submissions received each month but also ensure that your observation has sufficient information to make it useful for scientific inquiry. Files that do not meet the guidelines will unfortunately be ineligible for the ALPO galleries. Please feel free to contact the ALPO Comets Section coordinators for any questions you might have.

[i] Indexing is the abstracting of metadata from the observation (e.g., the observation date & time, the filter used, etc.) and associating it with the image/sketch so that it can be found by searching the metadata.